diff --git a/csharp/compatibility_tests/v3.0.0/protos/csharp/protos/unittest_issues.proto b/csharp/compatibility_tests/v3.0.0/protos/csharp/protos/unittest_issues.proto
new file mode 100644
index 0000000..6c9f763
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/protos/csharp/protos/unittest_issues.proto
@@ -0,0 +1,126 @@
+syntax = "proto3";
+
+// These proto descriptors have at one time been reported as an issue or defect.
+// They are kept here to replicate the issue, and continue to verify the fix.
+
+// Issue: Non-"Google.Protobuffers" namespace will ensure that protobuffer library types are qualified
+option csharp_namespace = "UnitTest.Issues.TestProtos";
+
+package unittest_issues;
+option optimize_for = SPEED;
+
+// Issue 307: when generating doubly-nested types, any references
+// should be of the form A.Types.B.Types.C.
+message Issue307 {
+  message NestedOnce {
+    message NestedTwice {
+    }
+  }
+}
+
+// Old issue 13: http://code.google.com/p/protobuf-csharp-port/issues/detail?id=13
+// New issue 309: https://github.com/google/protobuf/issues/309
+ 
+// message A {
+//    optional int32 _A = 1;
+// }
+
+// message B {
+//    optional int32 B_ = 1;
+// }
+
+//message AB {
+//    optional int32 a_b = 1;
+//}
+
+// Similar issue with numeric names
+// Java code failed too, so probably best for this to be a restriction.
+// See https://github.com/google/protobuf/issues/308
+// message NumberField {
+//    optional int32 _01 = 1;
+// }
+
+// issue 19 - negative enum values
+
+enum NegativeEnum {
+    NEGATIVE_ENUM_ZERO = 0;
+    FiveBelow = -5;
+    MinusOne = -1;
+}
+
+message NegativeEnumMessage {
+    NegativeEnum value = 1;
+    repeated NegativeEnum values = 2 [packed = false];
+    repeated NegativeEnum packed_values = 3 [packed=true];
+}
+
+// Issue 21: http://code.google.com/p/protobuf-csharp-port/issues/detail?id=21
+// Decorate fields with [deprecated=true] as [System.Obsolete]
+
+message DeprecatedChild {
+}
+
+enum DeprecatedEnum {
+    DEPRECATED_ZERO = 0;
+    one = 1;
+}
+
+message DeprecatedFieldsMessage {
+    int32 PrimitiveValue = 1 [deprecated = true];
+    repeated int32 PrimitiveArray = 2 [deprecated = true];
+
+    DeprecatedChild MessageValue = 3 [deprecated = true];
+    repeated DeprecatedChild MessageArray = 4 [deprecated = true];
+
+    DeprecatedEnum EnumValue = 5 [deprecated = true];
+    repeated DeprecatedEnum EnumArray = 6 [deprecated = true];
+}
+
+// Issue 45: http://code.google.com/p/protobuf-csharp-port/issues/detail?id=45
+message ItemField {
+  int32 item = 1;
+}
+
+message ReservedNames {
+  // Force a nested type called Types
+  message SomeNestedType {
+  }
+
+  int32 types = 1;
+  int32 descriptor = 2;
+}
+
+message TestJsonFieldOrdering {
+  // These fields are deliberately not declared in numeric
+  // order, and the oneof fields aren't contiguous either.
+  // This allows for reasonably robust tests of JSON output
+  // ordering.
+  // TestFieldOrderings in unittest_proto3.proto is similar,
+  // but doesn't include oneofs.
+  // TODO: Consider adding oneofs to TestFieldOrderings, although
+  // that will require fixing other tests in multiple platforms.
+  // Alternatively, consider just adding this to
+  // unittest_proto3.proto if multiple platforms want it.
+  
+  int32 plain_int32 = 4;
+
+  oneof o1 {
+    string o1_string = 2;
+    int32 o1_int32 = 5;
+  }
+  
+  string plain_string = 1;
+  
+  oneof o2 {
+    int32 o2_int32 = 6;
+    string o2_string = 3;
+  }
+  
+}
+
+message TestJsonName {
+  // Message for testing the effects for of the json_name option
+  string name = 1;
+  string description = 2 [json_name = "desc"];
+  string guid = 3 [json_name = "exid"];
+}
diff --git a/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/map_unittest_proto3.proto b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/map_unittest_proto3.proto
new file mode 100644
index 0000000..16be277
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/map_unittest_proto3.proto
@@ -0,0 +1,120 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This file is mostly equivalent to map_unittest.proto, but imports
+// unittest_proto3.proto instead of unittest.proto, so that it only
+// uses proto3 messages. This makes it suitable for testing
+// implementations which only support proto3.
+// The TestRequiredMessageMap message has been removed as there are no
+// required fields in proto3.
+syntax = "proto3";
+
+option cc_enable_arenas = true;
+option csharp_namespace = "Google.Protobuf.TestProtos";
+
+import "google/protobuf/unittest_proto3.proto";
+
+// We don't put this in a package within proto2 because we need to make sure
+// that the generated code doesn't depend on being in the proto2 namespace.
+// In map_test_util.h we do "using namespace unittest = protobuf_unittest".
+package protobuf_unittest;
+
+// Tests maps.
+message TestMap {
+  map<int32   , int32   > map_int32_int32       = 1;
+  map<int64   , int64   > map_int64_int64       = 2;
+  map<uint32  , uint32  > map_uint32_uint32     = 3;
+  map<uint64  , uint64  > map_uint64_uint64     = 4;
+  map<sint32  , sint32  > map_sint32_sint32     = 5;
+  map<sint64  , sint64  > map_sint64_sint64     = 6;
+  map<fixed32 , fixed32 > map_fixed32_fixed32   = 7;
+  map<fixed64 , fixed64 > map_fixed64_fixed64   = 8;
+  map<sfixed32, sfixed32> map_sfixed32_sfixed32 = 9;
+  map<sfixed64, sfixed64> map_sfixed64_sfixed64 = 10;
+  map<int32   , float   > map_int32_float       = 11;
+  map<int32   , double  > map_int32_double      = 12;
+  map<bool    , bool    > map_bool_bool         = 13;
+  map<string  , string  > map_string_string     = 14;
+  map<int32   , bytes   > map_int32_bytes       = 15;
+  map<int32   , MapEnum > map_int32_enum        = 16;
+  map<int32   , ForeignMessage> map_int32_foreign_message = 17;
+}
+
+message TestMapSubmessage {
+  TestMap test_map = 1;
+}
+
+message TestMessageMap {
+  map<int32, TestAllTypes> map_int32_message = 1;
+}
+
+// Two map fields share the same entry default instance.
+message TestSameTypeMap {
+  map<int32, int32> map1 = 1;
+  map<int32, int32> map2 = 2;
+}
+
+enum MapEnum {
+  MAP_ENUM_FOO = 0;
+  MAP_ENUM_BAR = 1;
+  MAP_ENUM_BAZ = 2;
+}
+
+message TestArenaMap {
+  map<int32   , int32   > map_int32_int32       = 1;
+  map<int64   , int64   > map_int64_int64       = 2;
+  map<uint32  , uint32  > map_uint32_uint32     = 3;
+  map<uint64  , uint64  > map_uint64_uint64     = 4;
+  map<sint32  , sint32  > map_sint32_sint32     = 5;
+  map<sint64  , sint64  > map_sint64_sint64     = 6;
+  map<fixed32 , fixed32 > map_fixed32_fixed32   = 7;
+  map<fixed64 , fixed64 > map_fixed64_fixed64   = 8;
+  map<sfixed32, sfixed32> map_sfixed32_sfixed32 = 9;
+  map<sfixed64, sfixed64> map_sfixed64_sfixed64 = 10;
+  map<int32   , float   > map_int32_float       = 11;
+  map<int32   , double  > map_int32_double      = 12;
+  map<bool    , bool    > map_bool_bool         = 13;
+  map<int32   , MapEnum > map_int32_enum        = 14;
+  map<int32   , ForeignMessage> map_int32_foreign_message = 15;
+}
+
+// Previously, message containing enum called Type cannot be used as value of
+// map field.
+message MessageContainingEnumCalledType {
+  enum Type {
+    TYPE_FOO = 0;
+  }
+  map<int32, MessageContainingEnumCalledType> type = 1;
+}
+
+// Previously, message cannot contain map field called "entry".
+message MessageContainingMapCalledEntry {
+  map<int32, int32> entry = 1;
+}
diff --git a/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_import_proto3.proto b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_import_proto3.proto
new file mode 100644
index 0000000..59673ea
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_import_proto3.proto
@@ -0,0 +1,68 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// A proto file which is imported by unittest_proto3.proto to test importing.
+
+syntax = "proto3";
+
+// We don't put this in a package within proto2 because we need to make sure
+// that the generated code doesn't depend on being in the proto2 namespace.
+// In test_util.h we do
+// "using namespace unittest_import = protobuf_unittest_import".
+package protobuf_unittest_import;
+
+option optimize_for = SPEED;
+option cc_enable_arenas = true;
+
+// Exercise the java_package option.
+option java_package = "com.google.protobuf.test";
+option csharp_namespace = "Google.Protobuf.TestProtos";
+
+// Do not set a java_outer_classname here to verify that Proto2 works without
+// one.
+
+// Test public import
+import public "google/protobuf/unittest_import_public_proto3.proto";
+
+message ImportMessage {
+  int32 d = 1;
+}
+
+enum ImportEnum {
+  IMPORT_ENUM_UNSPECIFIED = 0;
+  IMPORT_FOO = 7;
+  IMPORT_BAR = 8;
+  IMPORT_BAZ = 9;
+}
+
diff --git a/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_import_public_proto3.proto b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_import_public_proto3.proto
new file mode 100644
index 0000000..d6f11e2
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_import_public_proto3.proto
@@ -0,0 +1,42 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: liujisi@google.com (Pherl Liu)
+
+syntax = "proto3";
+
+package protobuf_unittest_import;
+
+option java_package = "com.google.protobuf.test";
+option csharp_namespace = "Google.Protobuf.TestProtos";
+
+message PublicImportMessage {
+ int32 e = 1;
+}
diff --git a/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_proto3.proto b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_proto3.proto
new file mode 100644
index 0000000..f59d217
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_proto3.proto
@@ -0,0 +1,388 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// A proto file we will use for unit testing.
+
+syntax = "proto3";
+
+// Some generic_services option(s) added automatically.
+// See:  http://go/proto2-generic-services-default
+option cc_generic_services = true;     // auto-added
+option java_generic_services = true;   // auto-added
+option py_generic_services = true;     // auto-added
+option cc_enable_arenas = true;
+option csharp_namespace = "Google.Protobuf.TestProtos";
+
+import "google/protobuf/unittest_import_proto3.proto";
+
+// We don't put this in a package within proto2 because we need to make sure
+// that the generated code doesn't depend on being in the proto2 namespace.
+// In test_util.h we do "using namespace unittest = protobuf_unittest".
+package protobuf_unittest;
+
+// Protos optimized for SPEED use a strict superset of the generated code
+// of equivalent ones optimized for CODE_SIZE, so we should optimize all our
+// tests for speed unless explicitly testing code size optimization.
+option optimize_for = SPEED;
+
+option java_outer_classname = "UnittestProto";
+
+// This proto includes every type of field in both singular and repeated
+// forms.
+message TestAllTypes {
+  message NestedMessage {
+    // The field name "b" fails to compile in proto1 because it conflicts with
+    // a local variable named "b" in one of the generated methods.  Doh.
+    // This file needs to compile in proto1 to test backwards-compatibility.
+    int32 bb = 1;
+  }
+
+  enum NestedEnum {
+    NESTED_ENUM_UNSPECIFIED = 0;
+    FOO = 1;
+    BAR = 2;
+    BAZ = 3;
+    NEG = -1;  // Intentionally negative.
+  }
+
+  // Singular
+  int32 single_int32 = 1;
+  int64 single_int64 = 2;
+  uint32 single_uint32 = 3;
+  uint64 single_uint64 = 4;
+  sint32 single_sint32 = 5;
+  sint64 single_sint64 = 6;
+  fixed32 single_fixed32 = 7;
+  fixed64 single_fixed64 = 8;
+  sfixed32 single_sfixed32 = 9;
+  sfixed64 single_sfixed64 = 10;
+  float single_float = 11;
+  double single_double = 12;
+  bool single_bool = 13;
+  string single_string = 14;
+  bytes single_bytes = 15;
+
+  NestedMessage single_nested_message = 18;
+  ForeignMessage single_foreign_message = 19;
+  protobuf_unittest_import.ImportMessage single_import_message = 20;
+
+  NestedEnum single_nested_enum = 21;
+  ForeignEnum single_foreign_enum = 22;
+  protobuf_unittest_import.ImportEnum single_import_enum = 23;
+
+  // Defined in unittest_import_public.proto
+  protobuf_unittest_import.PublicImportMessage
+      single_public_import_message = 26;
+
+  // Repeated
+  repeated    int32 repeated_int32    = 31;
+  repeated    int64 repeated_int64    = 32;
+  repeated   uint32 repeated_uint32   = 33;
+  repeated   uint64 repeated_uint64   = 34;
+  repeated   sint32 repeated_sint32   = 35;
+  repeated   sint64 repeated_sint64   = 36;
+  repeated  fixed32 repeated_fixed32  = 37;
+  repeated  fixed64 repeated_fixed64  = 38;
+  repeated sfixed32 repeated_sfixed32 = 39;
+  repeated sfixed64 repeated_sfixed64 = 40;
+  repeated    float repeated_float    = 41;
+  repeated   double repeated_double   = 42;
+  repeated     bool repeated_bool     = 43;
+  repeated   string repeated_string   = 44;
+  repeated    bytes repeated_bytes    = 45;
+
+  repeated NestedMessage                        repeated_nested_message  = 48;
+  repeated ForeignMessage                       repeated_foreign_message = 49;
+  repeated protobuf_unittest_import.ImportMessage repeated_import_message  = 50;
+
+  repeated NestedEnum                           repeated_nested_enum     = 51;
+  repeated ForeignEnum                          repeated_foreign_enum    = 52;
+  repeated protobuf_unittest_import.ImportEnum    repeated_import_enum     = 53;
+  // Defined in unittest_import_public.proto
+  repeated protobuf_unittest_import.PublicImportMessage
+      repeated_public_import_message = 54;
+
+  // For oneof test
+  oneof oneof_field {
+    uint32 oneof_uint32 = 111;
+    NestedMessage oneof_nested_message = 112;
+    string oneof_string = 113;
+    bytes oneof_bytes = 114;
+  }
+}
+
+// This proto includes a recusively nested message.
+message NestedTestAllTypes {
+  NestedTestAllTypes child = 1;
+  TestAllTypes payload = 2;
+  repeated NestedTestAllTypes repeated_child = 3;
+}
+
+message TestDeprecatedFields {
+  int32 deprecated_int32 = 1 [deprecated=true];
+}
+
+// Define these after TestAllTypes to make sure the compiler can handle
+// that.
+message ForeignMessage {
+  int32 c = 1;
+}
+
+enum ForeignEnum {
+  FOREIGN_UNSPECIFIED = 0;
+  FOREIGN_FOO = 4;
+  FOREIGN_BAR = 5;
+  FOREIGN_BAZ = 6;
+}
+
+message TestReservedFields {
+  reserved 2, 15, 9 to 11;
+  reserved "bar", "baz";
+}
+
+
+// Test that we can use NestedMessage from outside TestAllTypes.
+message TestForeignNested {
+  TestAllTypes.NestedMessage foreign_nested = 1;
+}
+
+// Test that really large tag numbers don't break anything.
+message TestReallyLargeTagNumber {
+  // The largest possible tag number is 2^28 - 1, since the wire format uses
+  // three bits to communicate wire type.
+  int32 a = 1;
+  int32 bb = 268435455;
+}
+
+message TestRecursiveMessage {
+  TestRecursiveMessage a = 1;
+  int32 i = 2;
+}
+
+// Test that mutual recursion works.
+message TestMutualRecursionA {
+  TestMutualRecursionB bb = 1;
+}
+
+message TestMutualRecursionB {
+  TestMutualRecursionA a = 1;
+  int32 optional_int32 = 2;
+}
+
+
+// Test an enum that has multiple values with the same number.
+enum TestEnumWithDupValue {
+  TEST_ENUM_WITH_DUP_VALUE_UNSPECIFIED = 0;
+  option allow_alias = true;
+
+  FOO1 = 1;
+  BAR1 = 2;
+  BAZ = 3;
+  FOO2 = 1;
+  BAR2 = 2;
+}
+
+// Test an enum with large, unordered values.
+enum TestSparseEnum {
+  TEST_SPARSE_ENUM_UNSPECIFIED = 0;
+  SPARSE_A = 123;
+  SPARSE_B = 62374;
+  SPARSE_C = 12589234;
+  SPARSE_D = -15;
+  SPARSE_E = -53452;
+  // In proto3, value 0 must be the first one specified
+  // SPARSE_F = 0;
+  SPARSE_G = 2;
+}
+
+// Test message with CamelCase field names.  This violates Protocol Buffer
+// standard style.
+message TestCamelCaseFieldNames {
+  int32 PrimitiveField = 1;
+  string StringField = 2;
+  ForeignEnum EnumField = 3;
+  ForeignMessage MessageField = 4;
+
+  repeated int32 RepeatedPrimitiveField = 7;
+  repeated string RepeatedStringField = 8;
+  repeated ForeignEnum RepeatedEnumField = 9;
+  repeated ForeignMessage RepeatedMessageField = 10;
+}
+
+
+// We list fields out of order, to ensure that we're using field number and not
+// field index to determine serialization order.
+message TestFieldOrderings {
+  string my_string = 11;
+  int64 my_int = 1;
+  float my_float = 101;
+  message NestedMessage {
+    int64 oo = 2;
+    // The field name "b" fails to compile in proto1 because it conflicts with
+    // a local variable named "b" in one of the generated methods.  Doh.
+    // This file needs to compile in proto1 to test backwards-compatibility.
+    int32 bb = 1;
+  }
+
+  NestedMessage single_nested_message  = 200;
+}
+
+message SparseEnumMessage {
+  TestSparseEnum sparse_enum = 1;
+}
+
+// Test String and Bytes: string is for valid UTF-8 strings
+message OneString {
+  string data = 1;
+}
+
+message MoreString {
+  repeated string data = 1;
+}
+
+message OneBytes {
+  bytes data = 1;
+}
+
+message MoreBytes {
+  bytes data = 1;
+}
+
+// Test int32, uint32, int64, uint64, and bool are all compatible
+message Int32Message {
+  int32 data = 1;
+}
+
+message Uint32Message {
+  uint32 data = 1;
+}
+
+message Int64Message {
+  int64 data = 1;
+}
+
+message Uint64Message {
+  uint64 data = 1;
+}
+
+message BoolMessage {
+  bool data = 1;
+}
+
+// Test oneofs.
+message TestOneof {
+  oneof foo {
+    int32 foo_int = 1;
+    string foo_string = 2;
+    TestAllTypes foo_message = 3;
+  }
+}
+
+// Test messages for packed fields
+
+message TestPackedTypes {
+  repeated    int32 packed_int32    =  90 [packed = true];
+  repeated    int64 packed_int64    =  91 [packed = true];
+  repeated   uint32 packed_uint32   =  92 [packed = true];
+  repeated   uint64 packed_uint64   =  93 [packed = true];
+  repeated   sint32 packed_sint32   =  94 [packed = true];
+  repeated   sint64 packed_sint64   =  95 [packed = true];
+  repeated  fixed32 packed_fixed32  =  96 [packed = true];
+  repeated  fixed64 packed_fixed64  =  97 [packed = true];
+  repeated sfixed32 packed_sfixed32 =  98 [packed = true];
+  repeated sfixed64 packed_sfixed64 =  99 [packed = true];
+  repeated    float packed_float    = 100 [packed = true];
+  repeated   double packed_double   = 101 [packed = true];
+  repeated     bool packed_bool     = 102 [packed = true];
+  repeated ForeignEnum packed_enum  = 103 [packed = true];
+}
+
+// A message with the same fields as TestPackedTypes, but without packing. Used
+// to test packed <-> unpacked wire compatibility.
+message TestUnpackedTypes {
+  repeated    int32 unpacked_int32    =  90 [packed = false];
+  repeated    int64 unpacked_int64    =  91 [packed = false];
+  repeated   uint32 unpacked_uint32   =  92 [packed = false];
+  repeated   uint64 unpacked_uint64   =  93 [packed = false];
+  repeated   sint32 unpacked_sint32   =  94 [packed = false];
+  repeated   sint64 unpacked_sint64   =  95 [packed = false];
+  repeated  fixed32 unpacked_fixed32  =  96 [packed = false];
+  repeated  fixed64 unpacked_fixed64  =  97 [packed = false];
+  repeated sfixed32 unpacked_sfixed32 =  98 [packed = false];
+  repeated sfixed64 unpacked_sfixed64 =  99 [packed = false];
+  repeated    float unpacked_float    = 100 [packed = false];
+  repeated   double unpacked_double   = 101 [packed = false];
+  repeated     bool unpacked_bool     = 102 [packed = false];
+  repeated ForeignEnum unpacked_enum  = 103 [packed = false];
+}
+
+message TestRepeatedScalarDifferentTagSizes {
+  // Parsing repeated fixed size values used to fail. This message needs to be
+  // used in order to get a tag of the right size; all of the repeated fields
+  // in TestAllTypes didn't trigger the check.
+  repeated fixed32 repeated_fixed32 = 12;
+  // Check for a varint type, just for good measure.
+  repeated int32   repeated_int32   = 13;
+
+  // These have two-byte tags.
+  repeated fixed64 repeated_fixed64 = 2046;
+  repeated int64   repeated_int64   = 2047;
+
+  // Three byte tags.
+  repeated float   repeated_float   = 262142;
+  repeated uint64  repeated_uint64  = 262143;
+}
+
+message TestCommentInjectionMessage {
+  // */ <- This should not close the generated doc comment
+  string a = 1;
+}
+
+
+// Test that RPC services work.
+message FooRequest  {}
+message FooResponse {}
+
+message FooClientMessage {}
+message FooServerMessage{}
+
+service TestService {
+  rpc Foo(FooRequest) returns (FooResponse);
+  rpc Bar(BarRequest) returns (BarResponse);
+}
+
+
+message BarRequest  {}
+message BarResponse {}
+
diff --git a/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_well_known_types.proto b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_well_known_types.proto
new file mode 100644
index 0000000..c907524
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/protos/src/google/protobuf/unittest_well_known_types.proto
@@ -0,0 +1,114 @@
+syntax = "proto3";
+
+package protobuf_unittest;
+
+option csharp_namespace = "Google.Protobuf.TestProtos";
+option java_multiple_files = true;
+option java_package = "com.google.protobuf.test";
+
+import "google/protobuf/any.proto";
+import "google/protobuf/api.proto";
+import "google/protobuf/duration.proto";
+import "google/protobuf/empty.proto";
+import "google/protobuf/field_mask.proto";
+import "google/protobuf/source_context.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/type.proto";
+import "google/protobuf/wrappers.proto";
+
+// Test that we can include all well-known types.
+// Each wrapper type is included separately, as languages
+// map handle different wrappers in different ways.
+message TestWellKnownTypes {
+  google.protobuf.Any any_field = 1;
+  google.protobuf.Api api_field = 2;
+  google.protobuf.Duration duration_field = 3;
+  google.protobuf.Empty empty_field = 4;
+  google.protobuf.FieldMask field_mask_field = 5;
+  google.protobuf.SourceContext source_context_field = 6;
+  google.protobuf.Struct struct_field = 7;
+  google.protobuf.Timestamp timestamp_field = 8;
+  google.protobuf.Type type_field = 9;
+  google.protobuf.DoubleValue double_field = 10;
+  google.protobuf.FloatValue float_field = 11;
+  google.protobuf.Int64Value int64_field = 12;
+  google.protobuf.UInt64Value uint64_field = 13;
+  google.protobuf.Int32Value int32_field = 14;
+  google.protobuf.UInt32Value uint32_field = 15;
+  google.protobuf.BoolValue bool_field = 16;
+  google.protobuf.StringValue string_field = 17;
+  google.protobuf.BytesValue bytes_field = 18;
+  // Part of struct, but useful to be able to test separately
+  google.protobuf.Value value_field = 19;
+}
+
+// A repeated field for each well-known type.
+message RepeatedWellKnownTypes {
+  repeated google.protobuf.Any any_field = 1;
+  repeated google.protobuf.Api api_field = 2;
+  repeated google.protobuf.Duration duration_field = 3;
+  repeated google.protobuf.Empty empty_field = 4;
+  repeated google.protobuf.FieldMask field_mask_field = 5;
+  repeated google.protobuf.SourceContext source_context_field = 6;
+  repeated google.protobuf.Struct struct_field = 7;
+  repeated google.protobuf.Timestamp timestamp_field = 8;
+  repeated google.protobuf.Type type_field = 9;
+  // These don't actually make a lot of sense, but they're not prohibited...
+  repeated google.protobuf.DoubleValue double_field = 10;
+  repeated google.protobuf.FloatValue float_field = 11;
+  repeated google.protobuf.Int64Value int64_field = 12;
+  repeated google.protobuf.UInt64Value uint64_field = 13;
+  repeated google.protobuf.Int32Value int32_field = 14;
+  repeated google.protobuf.UInt32Value uint32_field = 15;
+  repeated google.protobuf.BoolValue bool_field = 16;
+  repeated google.protobuf.StringValue string_field = 17;
+  repeated google.protobuf.BytesValue bytes_field = 18;
+}
+
+message OneofWellKnownTypes {
+  oneof oneof_field {
+    google.protobuf.Any any_field = 1;
+    google.protobuf.Api api_field = 2;
+    google.protobuf.Duration duration_field = 3;
+    google.protobuf.Empty empty_field = 4;
+    google.protobuf.FieldMask field_mask_field = 5;
+    google.protobuf.SourceContext source_context_field = 6;
+    google.protobuf.Struct struct_field = 7;
+    google.protobuf.Timestamp timestamp_field = 8;
+    google.protobuf.Type type_field = 9;
+    google.protobuf.DoubleValue double_field = 10;
+    google.protobuf.FloatValue float_field = 11;
+    google.protobuf.Int64Value int64_field = 12;
+    google.protobuf.UInt64Value uint64_field = 13;
+    google.protobuf.Int32Value int32_field = 14;
+    google.protobuf.UInt32Value uint32_field = 15;
+    google.protobuf.BoolValue bool_field = 16;
+    google.protobuf.StringValue string_field = 17;
+    google.protobuf.BytesValue bytes_field = 18;
+  }
+}
+
+// A map field for each well-known type. We only
+// need to worry about the value part of the map being the
+// well-known types, as messages can't be map keys.
+message MapWellKnownTypes {
+  map<int32,google.protobuf.Any> any_field = 1;
+  map<int32,google.protobuf.Api> api_field = 2;
+  map<int32,google.protobuf.Duration> duration_field = 3;
+  map<int32,google.protobuf.Empty> empty_field = 4;
+  map<int32,google.protobuf.FieldMask> field_mask_field = 5;
+  map<int32,google.protobuf.SourceContext> source_context_field = 6;
+  map<int32,google.protobuf.Struct> struct_field = 7;
+  map<int32,google.protobuf.Timestamp> timestamp_field = 8;
+  map<int32,google.protobuf.Type> type_field = 9;
+  map<int32,google.protobuf.DoubleValue> double_field = 10;
+  map<int32,google.protobuf.FloatValue> float_field = 11;
+  map<int32,google.protobuf.Int64Value> int64_field = 12;
+  map<int32,google.protobuf.UInt64Value> uint64_field = 13;
+  map<int32,google.protobuf.Int32Value> int32_field = 14;
+  map<int32,google.protobuf.UInt32Value> uint32_field = 15;
+  map<int32,google.protobuf.BoolValue> bool_field = 16;
+  map<int32,google.protobuf.StringValue> string_field = 17;
+  map<int32,google.protobuf.BytesValue> bytes_field = 18;
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/ByteStringTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/ByteStringTest.cs
new file mode 100644
index 0000000..685e130
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/ByteStringTest.cs
@@ -0,0 +1,171 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.Text;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class ByteStringTest
+    {
+        [Test]
+        public void Equality()
+        {
+            ByteString b1 = ByteString.CopyFrom(1, 2, 3);
+            ByteString b2 = ByteString.CopyFrom(1, 2, 3);
+            ByteString b3 = ByteString.CopyFrom(1, 2, 4);
+            ByteString b4 = ByteString.CopyFrom(1, 2, 3, 4);
+            EqualityTester.AssertEquality(b1, b1);
+            EqualityTester.AssertEquality(b1, b2);
+            EqualityTester.AssertInequality(b1, b3);
+            EqualityTester.AssertInequality(b1, b4);
+            EqualityTester.AssertInequality(b1, null);
+#pragma warning disable 1718 // Deliberately calling ==(b1, b1) and !=(b1, b1)
+            Assert.IsTrue(b1 == b1);
+            Assert.IsTrue(b1 == b2);
+            Assert.IsFalse(b1 == b3);
+            Assert.IsFalse(b1 == b4);
+            Assert.IsFalse(b1 == null);
+            Assert.IsTrue((ByteString) null == null);
+            Assert.IsFalse(b1 != b1);
+            Assert.IsFalse(b1 != b2);
+#pragma warning disable 1718
+            Assert.IsTrue(b1 != b3);
+            Assert.IsTrue(b1 != b4);
+            Assert.IsTrue(b1 != null);
+            Assert.IsFalse((ByteString) null != null);
+        }
+
+        [Test]
+        public void EmptyByteStringHasZeroSize()
+        {
+            Assert.AreEqual(0, ByteString.Empty.Length);
+        }
+
+        [Test]
+        public void CopyFromStringWithExplicitEncoding()
+        {
+            ByteString bs = ByteString.CopyFrom("AB", Encoding.Unicode);
+            Assert.AreEqual(4, bs.Length);
+            Assert.AreEqual(65, bs[0]);
+            Assert.AreEqual(0, bs[1]);
+            Assert.AreEqual(66, bs[2]);
+            Assert.AreEqual(0, bs[3]);
+        }
+
+        [Test]
+        public void IsEmptyWhenEmpty()
+        {
+            Assert.IsTrue(ByteString.CopyFromUtf8("").IsEmpty);
+        }
+
+        [Test]
+        public void IsEmptyWhenNotEmpty()
+        {
+            Assert.IsFalse(ByteString.CopyFromUtf8("X").IsEmpty);
+        }
+
+        [Test]
+        public void CopyFromByteArrayCopiesContents()
+        {
+            byte[] data = new byte[1];
+            data[0] = 10;
+            ByteString bs = ByteString.CopyFrom(data);
+            Assert.AreEqual(10, bs[0]);
+            data[0] = 5;
+            Assert.AreEqual(10, bs[0]);
+        }
+
+        [Test]
+        public void ToByteArrayCopiesContents()
+        {
+            ByteString bs = ByteString.CopyFromUtf8("Hello");
+            byte[] data = bs.ToByteArray();
+            Assert.AreEqual((byte)'H', data[0]);
+            Assert.AreEqual((byte)'H', bs[0]);
+            data[0] = 0;
+            Assert.AreEqual(0, data[0]);
+            Assert.AreEqual((byte)'H', bs[0]);
+        }
+
+        [Test]
+        public void CopyFromUtf8UsesUtf8()
+        {
+            ByteString bs = ByteString.CopyFromUtf8("\u20ac");
+            Assert.AreEqual(3, bs.Length);
+            Assert.AreEqual(0xe2, bs[0]);
+            Assert.AreEqual(0x82, bs[1]);
+            Assert.AreEqual(0xac, bs[2]);
+        }
+
+        [Test]
+        public void CopyFromPortion()
+        {
+            byte[] data = new byte[] {0, 1, 2, 3, 4, 5, 6};
+            ByteString bs = ByteString.CopyFrom(data, 2, 3);
+            Assert.AreEqual(3, bs.Length);
+            Assert.AreEqual(2, bs[0]);
+            Assert.AreEqual(3, bs[1]);
+        }
+
+        [Test]
+        public void ToStringUtf8()
+        {
+            ByteString bs = ByteString.CopyFromUtf8("\u20ac");
+            Assert.AreEqual("\u20ac", bs.ToStringUtf8());
+        }
+
+        [Test]
+        public void ToStringWithExplicitEncoding()
+        {
+            ByteString bs = ByteString.CopyFrom("\u20ac", Encoding.Unicode);
+            Assert.AreEqual("\u20ac", bs.ToString(Encoding.Unicode));
+        }
+
+        [Test]
+        public void FromBase64_WithText()
+        {
+            byte[] data = new byte[] {0, 1, 2, 3, 4, 5, 6};
+            string base64 = Convert.ToBase64String(data);
+            ByteString bs = ByteString.FromBase64(base64);
+            Assert.AreEqual(data, bs.ToByteArray());
+        }
+
+        [Test]
+        public void FromBase64_Empty()
+        {
+            // Optimization which also fixes issue 61.
+            Assert.AreSame(ByteString.Empty, ByteString.FromBase64(""));
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedInputStreamExtensions.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedInputStreamExtensions.cs
new file mode 100644
index 0000000..23af288
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedInputStreamExtensions.cs
@@ -0,0 +1,53 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    internal static class CodedInputStreamExtensions
+    {
+        public static void AssertNextTag(this CodedInputStream input, uint expectedTag)
+        {
+            uint tag = input.ReadTag();
+            Assert.AreEqual(expectedTag, tag);
+        }
+
+        public static T ReadMessage<T>(this CodedInputStream stream, MessageParser<T> parser)
+            where T : IMessage<T>
+        {
+            var message = parser.CreateTemplate();
+            stream.ReadMessage(message);
+            return message;
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedInputStreamTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedInputStreamTest.cs
new file mode 100644
index 0000000..ff44895
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedInputStreamTest.cs
@@ -0,0 +1,598 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.IO;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class CodedInputStreamTest
+    {
+        /// <summary>
+        /// Helper to construct a byte array from a bunch of bytes.  The inputs are
+        /// actually ints so that I can use hex notation and not get stupid errors
+        /// about precision.
+        /// </summary>
+        private static byte[] Bytes(params int[] bytesAsInts)
+        {
+            byte[] bytes = new byte[bytesAsInts.Length];
+            for (int i = 0; i < bytesAsInts.Length; i++)
+            {
+                bytes[i] = (byte) bytesAsInts[i];
+            }
+            return bytes;
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawVarint32() and ReadRawVarint64()
+        /// </summary>
+        private static void AssertReadVarint(byte[] data, ulong value)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            Assert.AreEqual((uint) value, input.ReadRawVarint32());
+
+            input = new CodedInputStream(data);
+            Assert.AreEqual(value, input.ReadRawVarint64());
+            Assert.IsTrue(input.IsAtEnd);
+
+            // Try different block sizes.
+            for (int bufferSize = 1; bufferSize <= 16; bufferSize *= 2)
+            {
+                input = new CodedInputStream(new SmallBlockInputStream(data, bufferSize));
+                Assert.AreEqual((uint) value, input.ReadRawVarint32());
+
+                input = new CodedInputStream(new SmallBlockInputStream(data, bufferSize));
+                Assert.AreEqual(value, input.ReadRawVarint64());
+                Assert.IsTrue(input.IsAtEnd);
+            }
+
+            // Try reading directly from a MemoryStream. We want to verify that it
+            // doesn't read past the end of the input, so write an extra byte - this
+            // lets us test the position at the end.
+            MemoryStream memoryStream = new MemoryStream();
+            memoryStream.Write(data, 0, data.Length);
+            memoryStream.WriteByte(0);
+            memoryStream.Position = 0;
+            Assert.AreEqual((uint) value, CodedInputStream.ReadRawVarint32(memoryStream));
+            Assert.AreEqual(data.Length, memoryStream.Position);
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawVarint32() and ReadRawVarint64() and
+        /// expects them to fail with an InvalidProtocolBufferException whose
+        /// description matches the given one.
+        /// </summary>
+        private static void AssertReadVarintFailure(InvalidProtocolBufferException expected, byte[] data)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            var exception = Assert.Throws<InvalidProtocolBufferException>(() => input.ReadRawVarint32());
+            Assert.AreEqual(expected.Message, exception.Message);
+
+            input = new CodedInputStream(data);
+            exception = Assert.Throws<InvalidProtocolBufferException>(() => input.ReadRawVarint64());
+            Assert.AreEqual(expected.Message, exception.Message);
+
+            // Make sure we get the same error when reading directly from a Stream.
+            exception = Assert.Throws<InvalidProtocolBufferException>(() => CodedInputStream.ReadRawVarint32(new MemoryStream(data)));
+            Assert.AreEqual(expected.Message, exception.Message);
+        }
+
+        [Test]
+        public void ReadVarint()
+        {
+            AssertReadVarint(Bytes(0x00), 0);
+            AssertReadVarint(Bytes(0x01), 1);
+            AssertReadVarint(Bytes(0x7f), 127);
+            // 14882
+            AssertReadVarint(Bytes(0xa2, 0x74), (0x22 << 0) | (0x74 << 7));
+            // 2961488830
+            AssertReadVarint(Bytes(0xbe, 0xf7, 0x92, 0x84, 0x0b),
+                             (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) |
+                             (0x0bL << 28));
+
+            // 64-bit
+            // 7256456126
+            AssertReadVarint(Bytes(0xbe, 0xf7, 0x92, 0x84, 0x1b),
+                             (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) |
+                             (0x1bL << 28));
+            // 41256202580718336
+            AssertReadVarint(Bytes(0x80, 0xe6, 0xeb, 0x9c, 0xc3, 0xc9, 0xa4, 0x49),
+                             (0x00 << 0) | (0x66 << 7) | (0x6b << 14) | (0x1c << 21) |
+                             (0x43L << 28) | (0x49L << 35) | (0x24L << 42) | (0x49L << 49));
+            // 11964378330978735131
+            AssertReadVarint(Bytes(0x9b, 0xa8, 0xf9, 0xc2, 0xbb, 0xd6, 0x80, 0x85, 0xa6, 0x01),
+                             (0x1b << 0) | (0x28 << 7) | (0x79 << 14) | (0x42 << 21) |
+                             (0x3bUL << 28) | (0x56UL << 35) | (0x00UL << 42) |
+                             (0x05UL << 49) | (0x26UL << 56) | (0x01UL << 63));
+
+            // Failures
+            AssertReadVarintFailure(
+                InvalidProtocolBufferException.MalformedVarint(),
+                Bytes(0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
+                      0x00));
+            AssertReadVarintFailure(
+                InvalidProtocolBufferException.TruncatedMessage(),
+                Bytes(0x80));
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawLittleEndian32() and checks
+        /// that the result matches the given value.
+        /// </summary>
+        private static void AssertReadLittleEndian32(byte[] data, uint value)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            Assert.AreEqual(value, input.ReadRawLittleEndian32());
+            Assert.IsTrue(input.IsAtEnd);
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize <= 16; blockSize *= 2)
+            {
+                input = new CodedInputStream(
+                    new SmallBlockInputStream(data, blockSize));
+                Assert.AreEqual(value, input.ReadRawLittleEndian32());
+                Assert.IsTrue(input.IsAtEnd);
+            }
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawLittleEndian64() and checks
+        /// that the result matches the given value.
+        /// </summary>
+        private static void AssertReadLittleEndian64(byte[] data, ulong value)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            Assert.AreEqual(value, input.ReadRawLittleEndian64());
+            Assert.IsTrue(input.IsAtEnd);
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize <= 16; blockSize *= 2)
+            {
+                input = new CodedInputStream(
+                    new SmallBlockInputStream(data, blockSize));
+                Assert.AreEqual(value, input.ReadRawLittleEndian64());
+                Assert.IsTrue(input.IsAtEnd);
+            }
+        }
+
+        [Test]
+        public void ReadLittleEndian()
+        {
+            AssertReadLittleEndian32(Bytes(0x78, 0x56, 0x34, 0x12), 0x12345678);
+            AssertReadLittleEndian32(Bytes(0xf0, 0xde, 0xbc, 0x9a), 0x9abcdef0);
+
+            AssertReadLittleEndian64(Bytes(0xf0, 0xde, 0xbc, 0x9a, 0x78, 0x56, 0x34, 0x12),
+                                     0x123456789abcdef0L);
+            AssertReadLittleEndian64(
+                Bytes(0x78, 0x56, 0x34, 0x12, 0xf0, 0xde, 0xbc, 0x9a), 0x9abcdef012345678UL);
+        }
+
+        [Test]
+        public void DecodeZigZag32()
+        {
+            Assert.AreEqual(0, CodedInputStream.DecodeZigZag32(0));
+            Assert.AreEqual(-1, CodedInputStream.DecodeZigZag32(1));
+            Assert.AreEqual(1, CodedInputStream.DecodeZigZag32(2));
+            Assert.AreEqual(-2, CodedInputStream.DecodeZigZag32(3));
+            Assert.AreEqual(0x3FFFFFFF, CodedInputStream.DecodeZigZag32(0x7FFFFFFE));
+            Assert.AreEqual(unchecked((int) 0xC0000000), CodedInputStream.DecodeZigZag32(0x7FFFFFFF));
+            Assert.AreEqual(0x7FFFFFFF, CodedInputStream.DecodeZigZag32(0xFFFFFFFE));
+            Assert.AreEqual(unchecked((int) 0x80000000), CodedInputStream.DecodeZigZag32(0xFFFFFFFF));
+        }
+
+        [Test]
+        public void DecodeZigZag64()
+        {
+            Assert.AreEqual(0, CodedInputStream.DecodeZigZag64(0));
+            Assert.AreEqual(-1, CodedInputStream.DecodeZigZag64(1));
+            Assert.AreEqual(1, CodedInputStream.DecodeZigZag64(2));
+            Assert.AreEqual(-2, CodedInputStream.DecodeZigZag64(3));
+            Assert.AreEqual(0x000000003FFFFFFFL, CodedInputStream.DecodeZigZag64(0x000000007FFFFFFEL));
+            Assert.AreEqual(unchecked((long) 0xFFFFFFFFC0000000L), CodedInputStream.DecodeZigZag64(0x000000007FFFFFFFL));
+            Assert.AreEqual(0x000000007FFFFFFFL, CodedInputStream.DecodeZigZag64(0x00000000FFFFFFFEL));
+            Assert.AreEqual(unchecked((long) 0xFFFFFFFF80000000L), CodedInputStream.DecodeZigZag64(0x00000000FFFFFFFFL));
+            Assert.AreEqual(0x7FFFFFFFFFFFFFFFL, CodedInputStream.DecodeZigZag64(0xFFFFFFFFFFFFFFFEL));
+            Assert.AreEqual(unchecked((long) 0x8000000000000000L), CodedInputStream.DecodeZigZag64(0xFFFFFFFFFFFFFFFFL));
+        }
+        
+        [Test]
+        public void ReadWholeMessage_VaryingBlockSizes()
+        {
+            TestAllTypes message = SampleMessages.CreateFullTestAllTypes();
+
+            byte[] rawBytes = message.ToByteArray();
+            Assert.AreEqual(rawBytes.Length, message.CalculateSize());
+            TestAllTypes message2 = TestAllTypes.Parser.ParseFrom(rawBytes);
+            Assert.AreEqual(message, message2);
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize < 256; blockSize *= 2)
+            {
+                message2 = TestAllTypes.Parser.ParseFrom(new SmallBlockInputStream(rawBytes, blockSize));
+                Assert.AreEqual(message, message2);
+            }
+        }
+                
+        [Test]
+        public void ReadHugeBlob()
+        {
+            // Allocate and initialize a 1MB blob.
+            byte[] blob = new byte[1 << 20];
+            for (int i = 0; i < blob.Length; i++)
+            {
+                blob[i] = (byte) i;
+            }
+
+            // Make a message containing it.
+            var message = new TestAllTypes { SingleBytes = ByteString.CopyFrom(blob) };
+
+            // Serialize and parse it.  Make sure to parse from an InputStream, not
+            // directly from a ByteString, so that CodedInputStream uses buffered
+            // reading.
+            TestAllTypes message2 = TestAllTypes.Parser.ParseFrom(message.ToByteString());
+
+            Assert.AreEqual(message, message2);
+        }
+
+        [Test]
+        public void ReadMaliciouslyLargeBlob()
+        {
+            MemoryStream ms = new MemoryStream();
+            CodedOutputStream output = new CodedOutputStream(ms);
+
+            uint tag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(tag);
+            output.WriteRawVarint32(0x7FFFFFFF);
+            output.WriteRawBytes(new byte[32]); // Pad with a few random bytes.
+            output.Flush();
+            ms.Position = 0;
+
+            CodedInputStream input = new CodedInputStream(ms);
+            Assert.AreEqual(tag, input.ReadTag());
+
+            Assert.Throws<InvalidProtocolBufferException>(() => input.ReadBytes());
+        }
+
+        internal static TestRecursiveMessage MakeRecursiveMessage(int depth)
+        {
+            if (depth == 0)
+            {
+                return new TestRecursiveMessage { I = 5 };
+            }
+            else
+            {
+                return new TestRecursiveMessage { A = MakeRecursiveMessage(depth - 1) };
+            }
+        }
+
+        internal static void AssertMessageDepth(TestRecursiveMessage message, int depth)
+        {
+            if (depth == 0)
+            {
+                Assert.IsNull(message.A);
+                Assert.AreEqual(5, message.I);
+            }
+            else
+            {
+                Assert.IsNotNull(message.A);
+                AssertMessageDepth(message.A, depth - 1);
+            }
+        }
+
+        [Test]
+        public void MaliciousRecursion()
+        {
+            ByteString data64 = MakeRecursiveMessage(64).ToByteString();
+            ByteString data65 = MakeRecursiveMessage(65).ToByteString();
+
+            AssertMessageDepth(TestRecursiveMessage.Parser.ParseFrom(data64), 64);
+
+            Assert.Throws<InvalidProtocolBufferException>(() => TestRecursiveMessage.Parser.ParseFrom(data65));
+
+            CodedInputStream input = CodedInputStream.CreateWithLimits(new MemoryStream(data64.ToByteArray()), 1000000, 63);
+            Assert.Throws<InvalidProtocolBufferException>(() => TestRecursiveMessage.Parser.ParseFrom(input));
+        }
+
+        [Test]
+        public void SizeLimit()
+        {
+            // Have to use a Stream rather than ByteString.CreateCodedInput as SizeLimit doesn't
+            // apply to the latter case.
+            MemoryStream ms = new MemoryStream(SampleMessages.CreateFullTestAllTypes().ToByteArray());
+            CodedInputStream input = CodedInputStream.CreateWithLimits(ms, 16, 100);
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseFrom(input));
+        }
+
+        /// <summary>
+        /// Tests that if we read an string that contains invalid UTF-8, no exception
+        /// is thrown.  Instead, the invalid bytes are replaced with the Unicode
+        /// "replacement character" U+FFFD.
+        /// </summary>
+        [Test]
+        public void ReadInvalidUtf8()
+        {
+            MemoryStream ms = new MemoryStream();
+            CodedOutputStream output = new CodedOutputStream(ms);
+
+            uint tag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(tag);
+            output.WriteRawVarint32(1);
+            output.WriteRawBytes(new byte[] {0x80});
+            output.Flush();
+            ms.Position = 0;
+
+            CodedInputStream input = new CodedInputStream(ms);
+
+            Assert.AreEqual(tag, input.ReadTag());
+            string text = input.ReadString();
+            Assert.AreEqual('\ufffd', text[0]);
+        }
+
+        /// <summary>
+        /// A stream which limits the number of bytes it reads at a time.
+        /// We use this to make sure that CodedInputStream doesn't screw up when
+        /// reading in small blocks.
+        /// </summary>
+        private sealed class SmallBlockInputStream : MemoryStream
+        {
+            private readonly int blockSize;
+
+            public SmallBlockInputStream(byte[] data, int blockSize)
+                : base(data)
+            {
+                this.blockSize = blockSize;
+            }
+
+            public override int Read(byte[] buffer, int offset, int count)
+            {
+                return base.Read(buffer, offset, Math.Min(count, blockSize));
+            }
+        }
+
+        [Test]
+        public void TestNegativeEnum()
+        {
+            byte[] bytes = { 0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x01 };
+            CodedInputStream input = new CodedInputStream(bytes);
+            Assert.AreEqual((int)SampleEnum.NegativeValue, input.ReadEnum());
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        //Issue 71:	CodedInputStream.ReadBytes go to slow path unnecessarily
+        [Test]
+        public void TestSlowPathAvoidance()
+        {
+            using (var ms = new MemoryStream())
+            {
+                CodedOutputStream output = new CodedOutputStream(ms);
+                output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+                output.WriteBytes(ByteString.CopyFrom(new byte[100]));
+                output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+                output.WriteBytes(ByteString.CopyFrom(new byte[100]));
+                output.Flush();
+
+                ms.Position = 0;
+                CodedInputStream input = new CodedInputStream(ms, new byte[ms.Length / 2], 0, 0, false);
+
+                uint tag = input.ReadTag();
+                Assert.AreEqual(1, WireFormat.GetTagFieldNumber(tag));
+                Assert.AreEqual(100, input.ReadBytes().Length);
+
+                tag = input.ReadTag();
+                Assert.AreEqual(2, WireFormat.GetTagFieldNumber(tag));
+                Assert.AreEqual(100, input.ReadBytes().Length);
+            }
+        }
+
+        [Test]
+        public void Tag0Throws()
+        {
+            var input = new CodedInputStream(new byte[] { 0 });
+            Assert.Throws<InvalidProtocolBufferException>(() => input.ReadTag());
+        }
+
+        [Test]
+        public void SkipGroup()
+        {
+            // Create an output stream with a group in:
+            // Field 1: string "field 1"
+            // Field 2: group containing:
+            //   Field 1: fixed int32 value 100
+            //   Field 2: string "ignore me"
+            //   Field 3: nested group containing
+            //      Field 1: fixed int64 value 1000
+            // Field 3: string "field 3"
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteString("field 1");
+            
+            // The outer group...
+            output.WriteTag(2, WireFormat.WireType.StartGroup);
+            output.WriteTag(1, WireFormat.WireType.Fixed32);
+            output.WriteFixed32(100);
+            output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+            output.WriteString("ignore me");
+            // The nested group...
+            output.WriteTag(3, WireFormat.WireType.StartGroup);
+            output.WriteTag(1, WireFormat.WireType.Fixed64);
+            output.WriteFixed64(1000);
+            // Note: Not sure the field number is relevant for end group...
+            output.WriteTag(3, WireFormat.WireType.EndGroup);
+
+            // End the outer group
+            output.WriteTag(2, WireFormat.WireType.EndGroup);
+
+            output.WriteTag(3, WireFormat.WireType.LengthDelimited);
+            output.WriteString("field 3");
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            Assert.AreEqual(WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited), input.ReadTag());
+            Assert.AreEqual("field 1", input.ReadString());
+            Assert.AreEqual(WireFormat.MakeTag(2, WireFormat.WireType.StartGroup), input.ReadTag());
+            input.SkipLastField(); // Should consume the whole group, including the nested one.
+            Assert.AreEqual(WireFormat.MakeTag(3, WireFormat.WireType.LengthDelimited), input.ReadTag());
+            Assert.AreEqual("field 3", input.ReadString());
+        }
+
+        [Test]
+        public void SkipGroup_WrongEndGroupTag()
+        {
+            // Create an output stream with:
+            // Field 1: string "field 1"
+            // Start group 2
+            //   Field 3: fixed int32
+            // End group 4 (should give an error)
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteString("field 1");
+
+            // The outer group...
+            output.WriteTag(2, WireFormat.WireType.StartGroup);
+            output.WriteTag(3, WireFormat.WireType.Fixed32);
+            output.WriteFixed32(100);
+            output.WriteTag(4, WireFormat.WireType.EndGroup);
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            Assert.AreEqual(WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited), input.ReadTag());
+            Assert.AreEqual("field 1", input.ReadString());
+            Assert.AreEqual(WireFormat.MakeTag(2, WireFormat.WireType.StartGroup), input.ReadTag());
+            Assert.Throws<InvalidProtocolBufferException>(input.SkipLastField);
+        }
+
+        [Test]
+        public void RogueEndGroupTag()
+        {
+            // If we have an end-group tag without a leading start-group tag, generated
+            // code will just call SkipLastField... so that should fail.
+
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(1, WireFormat.WireType.EndGroup);
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            Assert.AreEqual(WireFormat.MakeTag(1, WireFormat.WireType.EndGroup), input.ReadTag());
+            Assert.Throws<InvalidProtocolBufferException>(input.SkipLastField);
+        }
+
+        [Test]
+        public void EndOfStreamReachedWhileSkippingGroup()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(1, WireFormat.WireType.StartGroup);
+            output.WriteTag(2, WireFormat.WireType.StartGroup);
+            output.WriteTag(2, WireFormat.WireType.EndGroup);
+
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            input.ReadTag();
+            Assert.Throws<InvalidProtocolBufferException>(input.SkipLastField);
+        }
+
+        [Test]
+        public void RecursionLimitAppliedWhileSkippingGroup()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            for (int i = 0; i < CodedInputStream.DefaultRecursionLimit + 1; i++)
+            {
+                output.WriteTag(1, WireFormat.WireType.StartGroup);
+            }
+            for (int i = 0; i < CodedInputStream.DefaultRecursionLimit + 1; i++)
+            {
+                output.WriteTag(1, WireFormat.WireType.EndGroup);
+            }
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            Assert.AreEqual(WireFormat.MakeTag(1, WireFormat.WireType.StartGroup), input.ReadTag());
+            Assert.Throws<InvalidProtocolBufferException>(input.SkipLastField);
+        }
+
+        [Test]
+        public void Construction_Invalid()
+        {
+            Assert.Throws<ArgumentNullException>(() => new CodedInputStream((byte[]) null));
+            Assert.Throws<ArgumentNullException>(() => new CodedInputStream(null, 0, 0));
+            Assert.Throws<ArgumentNullException>(() => new CodedInputStream((Stream) null));
+            Assert.Throws<ArgumentOutOfRangeException>(() => new CodedInputStream(new byte[10], 100, 0));
+            Assert.Throws<ArgumentOutOfRangeException>(() => new CodedInputStream(new byte[10], 5, 10));
+        }
+
+        [Test]
+        public void CreateWithLimits_InvalidLimits()
+        {
+            var stream = new MemoryStream();
+            Assert.Throws<ArgumentOutOfRangeException>(() => CodedInputStream.CreateWithLimits(stream, 0, 1));
+            Assert.Throws<ArgumentOutOfRangeException>(() => CodedInputStream.CreateWithLimits(stream, 1, 0));
+        }
+
+        [Test]
+        public void Dispose_DisposesUnderlyingStream()
+        {
+            var memoryStream = new MemoryStream();
+            Assert.IsTrue(memoryStream.CanRead);
+            using (var cis = new CodedInputStream(memoryStream))
+            {
+            }
+            Assert.IsFalse(memoryStream.CanRead); // Disposed
+        }
+
+        [Test]
+        public void Dispose_WithLeaveOpen()
+        {
+            var memoryStream = new MemoryStream();
+            Assert.IsTrue(memoryStream.CanRead);
+            using (var cis = new CodedInputStream(memoryStream, true))
+            {
+            }
+            Assert.IsTrue(memoryStream.CanRead); // We left the stream open
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedOutputStreamTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedOutputStreamTest.cs
new file mode 100644
index 0000000..01bd321
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/CodedOutputStreamTest.cs
@@ -0,0 +1,419 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.IO;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class CodedOutputStreamTest
+    {
+        /// <summary>
+        /// Writes the given value using WriteRawVarint32() and WriteRawVarint64() and
+        /// checks that the result matches the given bytes
+        /// </summary>
+        private static void AssertWriteVarint(byte[] data, ulong value)
+        {
+            // Only do 32-bit write if the value fits in 32 bits.
+            if ((value >> 32) == 0)
+            {
+                MemoryStream rawOutput = new MemoryStream();
+                CodedOutputStream output = new CodedOutputStream(rawOutput);
+                output.WriteRawVarint32((uint) value);
+                output.Flush();
+                Assert.AreEqual(data, rawOutput.ToArray());
+                // Also try computing size.
+                Assert.AreEqual(data.Length, CodedOutputStream.ComputeRawVarint32Size((uint) value));
+            }
+
+            {
+                MemoryStream rawOutput = new MemoryStream();
+                CodedOutputStream output = new CodedOutputStream(rawOutput);
+                output.WriteRawVarint64(value);
+                output.Flush();
+                Assert.AreEqual(data, rawOutput.ToArray());
+
+                // Also try computing size.
+                Assert.AreEqual(data.Length, CodedOutputStream.ComputeRawVarint64Size(value));
+            }
+
+            // Try different buffer sizes.
+            for (int bufferSize = 1; bufferSize <= 16; bufferSize *= 2)
+            {
+                // Only do 32-bit write if the value fits in 32 bits.
+                if ((value >> 32) == 0)
+                {
+                    MemoryStream rawOutput = new MemoryStream();
+                    CodedOutputStream output =
+                        new CodedOutputStream(rawOutput, bufferSize);
+                    output.WriteRawVarint32((uint) value);
+                    output.Flush();
+                    Assert.AreEqual(data, rawOutput.ToArray());
+                }
+
+                {
+                    MemoryStream rawOutput = new MemoryStream();
+                    CodedOutputStream output = new CodedOutputStream(rawOutput, bufferSize);
+                    output.WriteRawVarint64(value);
+                    output.Flush();
+                    Assert.AreEqual(data, rawOutput.ToArray());
+                }
+            }
+        }
+
+        /// <summary>
+        /// Tests WriteRawVarint32() and WriteRawVarint64()
+        /// </summary>
+        [Test]
+        public void WriteVarint()
+        {
+            AssertWriteVarint(new byte[] {0x00}, 0);
+            AssertWriteVarint(new byte[] {0x01}, 1);
+            AssertWriteVarint(new byte[] {0x7f}, 127);
+            // 14882
+            AssertWriteVarint(new byte[] {0xa2, 0x74}, (0x22 << 0) | (0x74 << 7));
+            // 2961488830
+            AssertWriteVarint(new byte[] {0xbe, 0xf7, 0x92, 0x84, 0x0b},
+                              (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) |
+                              (0x0bL << 28));
+
+            // 64-bit
+            // 7256456126
+            AssertWriteVarint(new byte[] {0xbe, 0xf7, 0x92, 0x84, 0x1b},
+                              (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) |
+                              (0x1bL << 28));
+            // 41256202580718336
+            AssertWriteVarint(
+                new byte[] {0x80, 0xe6, 0xeb, 0x9c, 0xc3, 0xc9, 0xa4, 0x49},
+                (0x00 << 0) | (0x66 << 7) | (0x6b << 14) | (0x1c << 21) |
+                (0x43UL << 28) | (0x49L << 35) | (0x24UL << 42) | (0x49UL << 49));
+            // 11964378330978735131
+            AssertWriteVarint(
+                new byte[] {0x9b, 0xa8, 0xf9, 0xc2, 0xbb, 0xd6, 0x80, 0x85, 0xa6, 0x01},
+                unchecked((ulong)
+                          ((0x1b << 0) | (0x28 << 7) | (0x79 << 14) | (0x42 << 21) |
+                           (0x3bL << 28) | (0x56L << 35) | (0x00L << 42) |
+                           (0x05L << 49) | (0x26L << 56) | (0x01L << 63))));
+        }
+
+        /// <summary>
+        /// Parses the given bytes using WriteRawLittleEndian32() and checks
+        /// that the result matches the given value.
+        /// </summary>
+        private static void AssertWriteLittleEndian32(byte[] data, uint value)
+        {
+            MemoryStream rawOutput = new MemoryStream();
+            CodedOutputStream output = new CodedOutputStream(rawOutput);
+            output.WriteRawLittleEndian32(value);
+            output.Flush();
+            Assert.AreEqual(data, rawOutput.ToArray());
+
+            // Try different buffer sizes.
+            for (int bufferSize = 1; bufferSize <= 16; bufferSize *= 2)
+            {
+                rawOutput = new MemoryStream();
+                output = new CodedOutputStream(rawOutput, bufferSize);
+                output.WriteRawLittleEndian32(value);
+                output.Flush();
+                Assert.AreEqual(data, rawOutput.ToArray());
+            }
+        }
+
+        /// <summary>
+        /// Parses the given bytes using WriteRawLittleEndian64() and checks
+        /// that the result matches the given value.
+        /// </summary>
+        private static void AssertWriteLittleEndian64(byte[] data, ulong value)
+        {
+            MemoryStream rawOutput = new MemoryStream();
+            CodedOutputStream output = new CodedOutputStream(rawOutput);
+            output.WriteRawLittleEndian64(value);
+            output.Flush();
+            Assert.AreEqual(data, rawOutput.ToArray());
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize <= 16; blockSize *= 2)
+            {
+                rawOutput = new MemoryStream();
+                output = new CodedOutputStream(rawOutput, blockSize);
+                output.WriteRawLittleEndian64(value);
+                output.Flush();
+                Assert.AreEqual(data, rawOutput.ToArray());
+            }
+        }
+
+        /// <summary>
+        /// Tests writeRawLittleEndian32() and writeRawLittleEndian64().
+        /// </summary>
+        [Test]
+        public void WriteLittleEndian()
+        {
+            AssertWriteLittleEndian32(new byte[] {0x78, 0x56, 0x34, 0x12}, 0x12345678);
+            AssertWriteLittleEndian32(new byte[] {0xf0, 0xde, 0xbc, 0x9a}, 0x9abcdef0);
+
+            AssertWriteLittleEndian64(
+                new byte[] {0xf0, 0xde, 0xbc, 0x9a, 0x78, 0x56, 0x34, 0x12},
+                0x123456789abcdef0L);
+            AssertWriteLittleEndian64(
+                new byte[] {0x78, 0x56, 0x34, 0x12, 0xf0, 0xde, 0xbc, 0x9a},
+                0x9abcdef012345678UL);
+        }
+
+        [Test]
+        public void WriteWholeMessage_VaryingBlockSizes()
+        {
+            TestAllTypes message = SampleMessages.CreateFullTestAllTypes();
+
+            byte[] rawBytes = message.ToByteArray();
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize < 256; blockSize *= 2)
+            {
+                MemoryStream rawOutput = new MemoryStream();
+                CodedOutputStream output = new CodedOutputStream(rawOutput, blockSize);
+                message.WriteTo(output);
+                output.Flush();
+                Assert.AreEqual(rawBytes, rawOutput.ToArray());
+            }
+        }
+        
+        [Test]
+        public void EncodeZigZag32()
+        {
+            Assert.AreEqual(0u, CodedOutputStream.EncodeZigZag32(0));
+            Assert.AreEqual(1u, CodedOutputStream.EncodeZigZag32(-1));
+            Assert.AreEqual(2u, CodedOutputStream.EncodeZigZag32(1));
+            Assert.AreEqual(3u, CodedOutputStream.EncodeZigZag32(-2));
+            Assert.AreEqual(0x7FFFFFFEu, CodedOutputStream.EncodeZigZag32(0x3FFFFFFF));
+            Assert.AreEqual(0x7FFFFFFFu, CodedOutputStream.EncodeZigZag32(unchecked((int) 0xC0000000)));
+            Assert.AreEqual(0xFFFFFFFEu, CodedOutputStream.EncodeZigZag32(0x7FFFFFFF));
+            Assert.AreEqual(0xFFFFFFFFu, CodedOutputStream.EncodeZigZag32(unchecked((int) 0x80000000)));
+        }
+
+        [Test]
+        public void EncodeZigZag64()
+        {
+            Assert.AreEqual(0u, CodedOutputStream.EncodeZigZag64(0));
+            Assert.AreEqual(1u, CodedOutputStream.EncodeZigZag64(-1));
+            Assert.AreEqual(2u, CodedOutputStream.EncodeZigZag64(1));
+            Assert.AreEqual(3u, CodedOutputStream.EncodeZigZag64(-2));
+            Assert.AreEqual(0x000000007FFFFFFEuL,
+                            CodedOutputStream.EncodeZigZag64(unchecked((long) 0x000000003FFFFFFFUL)));
+            Assert.AreEqual(0x000000007FFFFFFFuL,
+                            CodedOutputStream.EncodeZigZag64(unchecked((long) 0xFFFFFFFFC0000000UL)));
+            Assert.AreEqual(0x00000000FFFFFFFEuL,
+                            CodedOutputStream.EncodeZigZag64(unchecked((long) 0x000000007FFFFFFFUL)));
+            Assert.AreEqual(0x00000000FFFFFFFFuL,
+                            CodedOutputStream.EncodeZigZag64(unchecked((long) 0xFFFFFFFF80000000UL)));
+            Assert.AreEqual(0xFFFFFFFFFFFFFFFEL,
+                            CodedOutputStream.EncodeZigZag64(unchecked((long) 0x7FFFFFFFFFFFFFFFUL)));
+            Assert.AreEqual(0xFFFFFFFFFFFFFFFFL,
+                            CodedOutputStream.EncodeZigZag64(unchecked((long) 0x8000000000000000UL)));
+        }
+
+        [Test]
+        public void RoundTripZigZag32()
+        {
+            // Some easier-to-verify round-trip tests.  The inputs (other than 0, 1, -1)
+            // were chosen semi-randomly via keyboard bashing.
+            Assert.AreEqual(0, CodedInputStream.DecodeZigZag32(CodedOutputStream.EncodeZigZag32(0)));
+            Assert.AreEqual(1, CodedInputStream.DecodeZigZag32(CodedOutputStream.EncodeZigZag32(1)));
+            Assert.AreEqual(-1, CodedInputStream.DecodeZigZag32(CodedOutputStream.EncodeZigZag32(-1)));
+            Assert.AreEqual(14927, CodedInputStream.DecodeZigZag32(CodedOutputStream.EncodeZigZag32(14927)));
+            Assert.AreEqual(-3612, CodedInputStream.DecodeZigZag32(CodedOutputStream.EncodeZigZag32(-3612)));
+        }
+
+        [Test]
+        public void RoundTripZigZag64()
+        {
+            Assert.AreEqual(0, CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(0)));
+            Assert.AreEqual(1, CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(1)));
+            Assert.AreEqual(-1, CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(-1)));
+            Assert.AreEqual(14927, CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(14927)));
+            Assert.AreEqual(-3612, CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(-3612)));
+
+            Assert.AreEqual(856912304801416L,
+                            CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(856912304801416L)));
+            Assert.AreEqual(-75123905439571256L,
+                            CodedInputStream.DecodeZigZag64(CodedOutputStream.EncodeZigZag64(-75123905439571256L)));
+        }
+
+        [Test]
+        public void TestNegativeEnumNoTag()
+        {
+            Assert.AreEqual(10, CodedOutputStream.ComputeInt32Size(-2));
+            Assert.AreEqual(10, CodedOutputStream.ComputeEnumSize((int) SampleEnum.NegativeValue));
+
+            byte[] bytes = new byte[10];
+            CodedOutputStream output = new CodedOutputStream(bytes);
+            output.WriteEnum((int) SampleEnum.NegativeValue);
+
+            Assert.AreEqual(0, output.SpaceLeft);
+            Assert.AreEqual("FE-FF-FF-FF-FF-FF-FF-FF-FF-01", BitConverter.ToString(bytes));
+        }
+
+        [Test]
+        public void TestCodedInputOutputPosition()
+        {
+            byte[] content = new byte[110];
+            for (int i = 0; i < content.Length; i++)
+                content[i] = (byte)i;
+
+            byte[] child = new byte[120];
+            {
+                MemoryStream ms = new MemoryStream(child);
+                CodedOutputStream cout = new CodedOutputStream(ms, 20);
+                // Field 11: numeric value: 500
+                cout.WriteTag(11, WireFormat.WireType.Varint);
+                Assert.AreEqual(1, cout.Position);
+                cout.WriteInt32(500);
+                Assert.AreEqual(3, cout.Position);
+                //Field 12: length delimited 120 bytes
+                cout.WriteTag(12, WireFormat.WireType.LengthDelimited);
+                Assert.AreEqual(4, cout.Position);
+                cout.WriteBytes(ByteString.CopyFrom(content));
+                Assert.AreEqual(115, cout.Position);
+                // Field 13: fixed numeric value: 501
+                cout.WriteTag(13, WireFormat.WireType.Fixed32);
+                Assert.AreEqual(116, cout.Position);
+                cout.WriteSFixed32(501);
+                Assert.AreEqual(120, cout.Position);
+                cout.Flush();
+            }
+
+            byte[] bytes = new byte[130];
+            {
+                CodedOutputStream cout = new CodedOutputStream(bytes);
+                // Field 1: numeric value: 500
+                cout.WriteTag(1, WireFormat.WireType.Varint);
+                Assert.AreEqual(1, cout.Position);
+                cout.WriteInt32(500);
+                Assert.AreEqual(3, cout.Position);
+                //Field 2: length delimited 120 bytes
+                cout.WriteTag(2, WireFormat.WireType.LengthDelimited);
+                Assert.AreEqual(4, cout.Position);
+                cout.WriteBytes(ByteString.CopyFrom(child));
+                Assert.AreEqual(125, cout.Position);
+                // Field 3: fixed numeric value: 500
+                cout.WriteTag(3, WireFormat.WireType.Fixed32);
+                Assert.AreEqual(126, cout.Position);
+                cout.WriteSFixed32(501);
+                Assert.AreEqual(130, cout.Position);
+                cout.Flush();
+            }
+            // Now test Input stream:
+            {
+                CodedInputStream cin = new CodedInputStream(new MemoryStream(bytes), new byte[50], 0, 0, false);
+                Assert.AreEqual(0, cin.Position);
+                // Field 1:
+                uint tag = cin.ReadTag();
+                Assert.AreEqual(1, tag >> 3);
+                Assert.AreEqual(1, cin.Position);
+                Assert.AreEqual(500, cin.ReadInt32());
+                Assert.AreEqual(3, cin.Position);
+                //Field 2:
+                tag = cin.ReadTag();
+                Assert.AreEqual(2, tag >> 3);
+                Assert.AreEqual(4, cin.Position);
+                int childlen = cin.ReadLength();
+                Assert.AreEqual(120, childlen);
+                Assert.AreEqual(5, cin.Position);
+                int oldlimit = cin.PushLimit((int)childlen);
+                Assert.AreEqual(5, cin.Position);
+                // Now we are reading child message
+                {
+                    // Field 11: numeric value: 500
+                    tag = cin.ReadTag();
+                    Assert.AreEqual(11, tag >> 3);
+                    Assert.AreEqual(6, cin.Position);
+                    Assert.AreEqual(500, cin.ReadInt32());
+                    Assert.AreEqual(8, cin.Position);
+                    //Field 12: length delimited 120 bytes
+                    tag = cin.ReadTag();
+                    Assert.AreEqual(12, tag >> 3);
+                    Assert.AreEqual(9, cin.Position);
+                    ByteString bstr = cin.ReadBytes();
+                    Assert.AreEqual(110, bstr.Length);
+                    Assert.AreEqual((byte) 109, bstr[109]);
+                    Assert.AreEqual(120, cin.Position);
+                    // Field 13: fixed numeric value: 501
+                    tag = cin.ReadTag();
+                    Assert.AreEqual(13, tag >> 3);
+                    // ROK - Previously broken here, this returned 126 failing to account for bufferSizeAfterLimit
+                    Assert.AreEqual(121, cin.Position);
+                    Assert.AreEqual(501, cin.ReadSFixed32());
+                    Assert.AreEqual(125, cin.Position);
+                    Assert.IsTrue(cin.IsAtEnd);
+                }
+                cin.PopLimit(oldlimit);
+                Assert.AreEqual(125, cin.Position);
+                // Field 3: fixed numeric value: 501
+                tag = cin.ReadTag();
+                Assert.AreEqual(3, tag >> 3);
+                Assert.AreEqual(126, cin.Position);
+                Assert.AreEqual(501, cin.ReadSFixed32());
+                Assert.AreEqual(130, cin.Position);
+                Assert.IsTrue(cin.IsAtEnd);
+            }
+        }
+
+        [Test]
+        public void Dispose_DisposesUnderlyingStream()
+        {
+            var memoryStream = new MemoryStream();
+            Assert.IsTrue(memoryStream.CanWrite);
+            using (var cos = new CodedOutputStream(memoryStream))
+            {
+                cos.WriteRawByte(0);
+                Assert.AreEqual(0, memoryStream.Position); // Not flushed yet
+            }
+            Assert.AreEqual(1, memoryStream.ToArray().Length); // Flushed data from CodedOutputStream to MemoryStream
+            Assert.IsFalse(memoryStream.CanWrite); // Disposed
+        }
+
+        [Test]
+        public void Dispose_WithLeaveOpen()
+        {
+            var memoryStream = new MemoryStream();
+            Assert.IsTrue(memoryStream.CanWrite);
+            using (var cos = new CodedOutputStream(memoryStream, true))
+            {
+                cos.WriteRawByte(0);
+                Assert.AreEqual(0, memoryStream.Position); // Not flushed yet
+            }
+            Assert.AreEqual(1, memoryStream.Position); // Flushed data from CodedOutputStream to MemoryStream
+            Assert.IsTrue(memoryStream.CanWrite); // We left the stream open
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Collections/MapFieldTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Collections/MapFieldTest.cs
new file mode 100644
index 0000000..9c84590
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Collections/MapFieldTest.cs
@@ -0,0 +1,532 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.Collections.Generic;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+using System.Collections;
+using System.Linq;
+
+namespace Google.Protobuf.Collections
+{
+    /// <summary>
+    /// Tests for MapField which aren't reliant on the encoded format -
+    /// tests for serialization/deserialization are part of GeneratedMessageTest.
+    /// </summary>
+    public class MapFieldTest
+    {
+        [Test]
+        public void Clone_ClonesMessages()
+        {
+            var message = new ForeignMessage { C = 20 };
+            var map = new MapField<string, ForeignMessage> { { "x", message } };
+            var clone = map.Clone();
+            map["x"].C = 30;
+            Assert.AreEqual(20, clone["x"].C);
+        }
+
+        [Test]
+        public void NullValuesProhibited()
+        {
+            TestNullValues<int?>(0);
+            TestNullValues("");
+            TestNullValues(new TestAllTypes());
+        }
+
+        private void TestNullValues<T>(T nonNullValue)
+        {
+            var map = new MapField<int, T>();
+            var nullValue = (T) (object) null;
+            Assert.Throws<ArgumentNullException>(() => map.Add(0, nullValue));
+            Assert.Throws<ArgumentNullException>(() => map[0] = nullValue);
+            map.Add(1, nonNullValue);
+            map[1] = nonNullValue;
+        }
+
+        [Test]
+        public void Add_ForbidsNullKeys()
+        {
+            var map = new MapField<string, ForeignMessage>();
+            Assert.Throws<ArgumentNullException>(() => map.Add(null, new ForeignMessage()));
+        }
+
+        [Test]
+        public void Indexer_ForbidsNullKeys()
+        {
+            var map = new MapField<string, ForeignMessage>();
+            Assert.Throws<ArgumentNullException>(() => map[null] = new ForeignMessage());
+        }
+        
+        [Test]
+        public void AddPreservesInsertionOrder()
+        {
+            var map = new MapField<string, string>();
+            map.Add("a", "v1");
+            map.Add("b", "v2");
+            map.Add("c", "v3");
+            map.Remove("b");
+            map.Add("d", "v4");
+            CollectionAssert.AreEqual(new[] { "a", "c", "d" }, map.Keys);
+            CollectionAssert.AreEqual(new[] { "v1", "v3", "v4" }, map.Values);
+        }
+
+        [Test]
+        public void EqualityIsOrderInsensitive()
+        {
+            var map1 = new MapField<string, string>();
+            map1.Add("a", "v1");
+            map1.Add("b", "v2");
+
+            var map2 = new MapField<string, string>();
+            map2.Add("b", "v2");
+            map2.Add("a", "v1");
+
+            EqualityTester.AssertEquality(map1, map2);
+        }
+
+        [Test]
+        public void EqualityIsKeySensitive()
+        {
+            var map1 = new MapField<string, string>();
+            map1.Add("first key", "v1");
+            map1.Add("second key", "v2");
+
+            var map2 = new MapField<string, string>();
+            map2.Add("third key", "v1");
+            map2.Add("fourth key", "v2");
+
+            EqualityTester.AssertInequality(map1, map2);
+        }
+
+        [Test]
+        public void Equality_Simple()
+        {
+            var map = new MapField<string, string>();
+            EqualityTester.AssertEquality(map, map);
+            EqualityTester.AssertInequality(map, null);
+            Assert.IsFalse(map.Equals(new object()));
+        }
+
+        [Test]
+        public void EqualityIsValueSensitive()
+        {
+            // Note: Without some care, it's a little easier than one might
+            // hope to see hash collisions, but only in some environments...
+            var map1 = new MapField<string, string>();
+            map1.Add("a", "first value");
+            map1.Add("b", "second value");
+
+            var map2 = new MapField<string, string>();
+            map2.Add("a", "third value");
+            map2.Add("b", "fourth value");
+
+            EqualityTester.AssertInequality(map1, map2);
+        }
+
+        [Test]
+        public void Add_Dictionary()
+        {
+            var map1 = new MapField<string, string>
+            {
+                { "x", "y" },
+                { "a", "b" }
+            };
+            var map2 = new MapField<string, string>
+            {
+                { "before", "" },
+                map1,
+                { "after", "" }
+            };
+            var expected = new MapField<string, string>
+            {
+                { "before", "" },
+                { "x", "y" },
+                { "a", "b" },
+                { "after", "" }
+            };
+            Assert.AreEqual(expected, map2);
+            CollectionAssert.AreEqual(new[] { "before", "x", "a", "after" }, map2.Keys);
+        }
+
+        // General IDictionary<TKey, TValue> behavior tests
+        [Test]
+        public void Add_KeyAlreadyExists()
+        {
+            var map = new MapField<string, string>();
+            map.Add("foo", "bar");
+            Assert.Throws<ArgumentException>(() => map.Add("foo", "baz"));
+        }
+
+        [Test]
+        public void Add_Pair()
+        {
+            var map = new MapField<string, string>();
+            ICollection<KeyValuePair<string, string>> collection = map;
+            collection.Add(NewKeyValuePair("x", "y"));
+            Assert.AreEqual("y", map["x"]);
+            Assert.Throws<ArgumentException>(() => collection.Add(NewKeyValuePair("x", "z")));
+        }
+
+        [Test]
+        public void Contains_Pair()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            ICollection<KeyValuePair<string, string>> collection = map;
+            Assert.IsTrue(collection.Contains(NewKeyValuePair("x", "y")));
+            Assert.IsFalse(collection.Contains(NewKeyValuePair("x", "z")));
+            Assert.IsFalse(collection.Contains(NewKeyValuePair("z", "y")));
+        }
+
+        [Test]
+        public void Remove_Key()
+        {
+            var map = new MapField<string, string>();
+            map.Add("foo", "bar");
+            Assert.AreEqual(1, map.Count);
+            Assert.IsFalse(map.Remove("missing"));
+            Assert.AreEqual(1, map.Count);
+            Assert.IsTrue(map.Remove("foo"));
+            Assert.AreEqual(0, map.Count);
+            Assert.Throws<ArgumentNullException>(() => map.Remove(null));
+        }
+
+        [Test]
+        public void Remove_Pair()
+        {
+            var map = new MapField<string, string>();
+            map.Add("foo", "bar");
+            ICollection<KeyValuePair<string, string>> collection = map;
+            Assert.AreEqual(1, map.Count);
+            Assert.IsFalse(collection.Remove(NewKeyValuePair("wrong key", "bar")));
+            Assert.AreEqual(1, map.Count);
+            Assert.IsFalse(collection.Remove(NewKeyValuePair("foo", "wrong value")));
+            Assert.AreEqual(1, map.Count);
+            Assert.IsTrue(collection.Remove(NewKeyValuePair("foo", "bar")));
+            Assert.AreEqual(0, map.Count);
+            Assert.Throws<ArgumentException>(() => collection.Remove(new KeyValuePair<string, string>(null, "")));
+        }
+
+        [Test]
+        public void CopyTo_Pair()
+        {
+            var map = new MapField<string, string>();
+            map.Add("foo", "bar");
+            ICollection<KeyValuePair<string, string>> collection = map;
+            KeyValuePair<string, string>[] array = new KeyValuePair<string, string>[3];
+            collection.CopyTo(array, 1);
+            Assert.AreEqual(NewKeyValuePair("foo", "bar"), array[1]);
+        }
+
+        [Test]
+        public void Clear()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            Assert.AreEqual(1, map.Count);
+            map.Clear();
+            Assert.AreEqual(0, map.Count);
+            map.Add("x", "y");
+            Assert.AreEqual(1, map.Count);
+        }
+
+        [Test]
+        public void Indexer_Get()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            Assert.AreEqual("y", map["x"]);
+            Assert.Throws<KeyNotFoundException>(() => { var ignored = map["z"]; });
+        }
+
+        [Test]
+        public void Indexer_Set()
+        {
+            var map = new MapField<string, string>();
+            map["x"] = "y";
+            Assert.AreEqual("y", map["x"]);
+            map["x"] = "z"; // This won't throw, unlike Add.
+            Assert.AreEqual("z", map["x"]);
+        }
+
+        [Test]
+        public void GetEnumerator_NonGeneric()
+        {
+            IEnumerable map = new MapField<string, string> { { "x", "y" } };
+            CollectionAssert.AreEqual(new[] { new KeyValuePair<string, string>("x", "y") },
+                map.Cast<object>().ToList());
+        }
+
+        // Test for the explicitly-implemented non-generic IDictionary interface
+        [Test]
+        public void IDictionary_GetEnumerator()
+        {
+            IDictionary map = new MapField<string, string> { { "x", "y" } };
+            var enumerator = map.GetEnumerator();
+
+            // Commented assertions show an ideal situation - it looks like
+            // the LinkedList enumerator doesn't throw when you ask for the current entry
+            // at an inappropriate time; fixing this would be more work than it's worth.
+            // Assert.Throws<InvalidOperationException>(() => enumerator.Current.GetHashCode());
+            Assert.IsTrue(enumerator.MoveNext());
+            Assert.AreEqual("x", enumerator.Key);
+            Assert.AreEqual("y", enumerator.Value);
+            Assert.AreEqual(new DictionaryEntry("x", "y"), enumerator.Current);
+            Assert.AreEqual(new DictionaryEntry("x", "y"), enumerator.Entry);
+            Assert.IsFalse(enumerator.MoveNext());
+            // Assert.Throws<InvalidOperationException>(() => enumerator.Current.GetHashCode());
+            enumerator.Reset();
+            // Assert.Throws<InvalidOperationException>(() => enumerator.Current.GetHashCode());
+            Assert.IsTrue(enumerator.MoveNext());
+            Assert.AreEqual("x", enumerator.Key); // Assume the rest are okay
+        }
+
+        [Test]
+        public void IDictionary_Add()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            IDictionary dictionary = map;
+            dictionary.Add("a", "b");
+            Assert.AreEqual("b", map["a"]);
+            Assert.Throws<ArgumentException>(() => dictionary.Add("a", "duplicate"));
+            Assert.Throws<InvalidCastException>(() => dictionary.Add(new object(), "key is bad"));
+            Assert.Throws<InvalidCastException>(() => dictionary.Add("value is bad", new object()));
+        }
+
+        [Test]
+        public void IDictionary_Contains()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            IDictionary dictionary = map;
+
+            Assert.IsFalse(dictionary.Contains("a"));
+            Assert.IsFalse(dictionary.Contains(5));
+            // Surprising, but IDictionary.Contains is only about keys.
+            Assert.IsFalse(dictionary.Contains(new DictionaryEntry("x", "y")));
+            Assert.IsTrue(dictionary.Contains("x"));
+        }
+
+        [Test]
+        public void IDictionary_Remove()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            IDictionary dictionary = map;
+            dictionary.Remove("a");
+            Assert.AreEqual(1, dictionary.Count);
+            dictionary.Remove(5);
+            Assert.AreEqual(1, dictionary.Count);
+            dictionary.Remove(new DictionaryEntry("x", "y"));
+            Assert.AreEqual(1, dictionary.Count);
+            dictionary.Remove("x");
+            Assert.AreEqual(0, dictionary.Count);
+            Assert.Throws<ArgumentNullException>(() => dictionary.Remove(null));
+        }
+
+        [Test]
+        public void IDictionary_CopyTo()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            IDictionary dictionary = map;
+            var array = new DictionaryEntry[3];
+            dictionary.CopyTo(array, 1);
+            CollectionAssert.AreEqual(new[] { default(DictionaryEntry), new DictionaryEntry("x", "y"), default(DictionaryEntry) },
+                array);
+            var objectArray = new object[3];
+            dictionary.CopyTo(objectArray, 1);
+            CollectionAssert.AreEqual(new object[] { null, new DictionaryEntry("x", "y"), null },
+                objectArray);
+        }
+
+        [Test]
+        public void IDictionary_IsFixedSize()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            IDictionary dictionary = map;
+            Assert.IsFalse(dictionary.IsFixedSize);
+        }
+
+        [Test]
+        public void IDictionary_Keys()
+        {
+            IDictionary dictionary = new MapField<string, string> { { "x", "y" } };
+            CollectionAssert.AreEqual(new[] { "x" }, dictionary.Keys);
+        }
+
+        [Test]
+        public void IDictionary_Values()
+        {
+            IDictionary dictionary = new MapField<string, string> { { "x", "y" } };
+            CollectionAssert.AreEqual(new[] { "y" }, dictionary.Values);
+        }
+
+        [Test]
+        public void IDictionary_IsSynchronized()
+        {
+            IDictionary dictionary = new MapField<string, string> { { "x", "y" } };
+            Assert.IsFalse(dictionary.IsSynchronized);
+        }
+
+        [Test]
+        public void IDictionary_SyncRoot()
+        {
+            IDictionary dictionary = new MapField<string, string> { { "x", "y" } };
+            Assert.AreSame(dictionary, dictionary.SyncRoot);
+        }
+
+        [Test]
+        public void IDictionary_Indexer_Get()
+        {
+            IDictionary dictionary = new MapField<string, string> { { "x", "y" } };
+            Assert.AreEqual("y", dictionary["x"]);
+            Assert.IsNull(dictionary["a"]);
+            Assert.IsNull(dictionary[5]);
+            Assert.Throws<ArgumentNullException>(() => dictionary[null].GetHashCode());
+        }
+
+        [Test]
+        public void IDictionary_Indexer_Set()
+        {
+            var map = new MapField<string, string> { { "x", "y" } };
+            IDictionary dictionary = map;
+            map["a"] = "b";
+            Assert.AreEqual("b", map["a"]);
+            map["a"] = "c";
+            Assert.AreEqual("c", map["a"]);
+            Assert.Throws<InvalidCastException>(() => dictionary[5] = "x");
+            Assert.Throws<InvalidCastException>(() => dictionary["x"] = 5);
+            Assert.Throws<ArgumentNullException>(() => dictionary[null] = "z");
+            Assert.Throws<ArgumentNullException>(() => dictionary["x"] = null);
+        }
+
+        [Test]
+        public void KeysReturnsLiveView()
+        {
+            var map = new MapField<string, string>();
+            var keys = map.Keys;
+            CollectionAssert.AreEqual(new string[0], keys);
+            map["foo"] = "bar";
+            map["x"] = "y";
+            CollectionAssert.AreEqual(new[] { "foo", "x" }, keys);
+        }
+
+        [Test]
+        public void ValuesReturnsLiveView()
+        {
+            var map = new MapField<string, string>();
+            var values = map.Values;
+            CollectionAssert.AreEqual(new string[0], values);
+            map["foo"] = "bar";
+            map["x"] = "y";
+            CollectionAssert.AreEqual(new[] { "bar", "y" }, values);
+        }
+
+        // Just test keys - we know the implementation is the same for values
+        [Test]
+        public void ViewsAreReadOnly()
+        {
+            var map = new MapField<string, string>();
+            var keys = map.Keys;
+            Assert.IsTrue(keys.IsReadOnly);
+            Assert.Throws<NotSupportedException>(() => keys.Clear());
+            Assert.Throws<NotSupportedException>(() => keys.Remove("a"));
+            Assert.Throws<NotSupportedException>(() => keys.Add("a"));
+        }
+
+        // Just test keys - we know the implementation is the same for values
+        [Test]
+        public void ViewCopyTo()
+        {
+            var map = new MapField<string, string> { { "foo", "bar" }, { "x", "y" } };
+            var keys = map.Keys;
+            var array = new string[4];
+            Assert.Throws<ArgumentException>(() => keys.CopyTo(array, 3));
+            Assert.Throws<ArgumentOutOfRangeException>(() => keys.CopyTo(array, -1));
+            keys.CopyTo(array, 1);
+            CollectionAssert.AreEqual(new[] { null, "foo", "x", null }, array);
+        }
+        
+        // Just test keys - we know the implementation is the same for values
+        [Test]
+        public void NonGenericViewCopyTo()
+        {
+            IDictionary map = new MapField<string, string> { { "foo", "bar" }, { "x", "y" } };
+            ICollection keys = map.Keys;
+            // Note the use of the Array type here rather than string[]
+            Array array = new string[4];
+            Assert.Throws<ArgumentException>(() => keys.CopyTo(array, 3));
+            Assert.Throws<ArgumentOutOfRangeException>(() => keys.CopyTo(array, -1));
+            keys.CopyTo(array, 1);
+            CollectionAssert.AreEqual(new[] { null, "foo", "x", null }, array);
+        }
+
+        [Test]
+        public void KeysContains()
+        {
+            var map = new MapField<string, string> { { "foo", "bar" }, { "x", "y" } };
+            var keys = map.Keys;
+            Assert.IsTrue(keys.Contains("foo"));
+            Assert.IsFalse(keys.Contains("bar")); // It's a value!
+            Assert.IsFalse(keys.Contains("1"));
+            // Keys can't be null, so we should prevent contains check
+            Assert.Throws<ArgumentNullException>(() => keys.Contains(null));
+        }
+
+        [Test]
+        public void ValuesContains()
+        {
+            var map = new MapField<string, string> { { "foo", "bar" }, { "x", "y" } };
+            var values = map.Values;
+            Assert.IsTrue(values.Contains("bar"));
+            Assert.IsFalse(values.Contains("foo")); // It's a key!
+            Assert.IsFalse(values.Contains("1"));
+            // Values can be null, so this makes sense
+            Assert.IsFalse(values.Contains(null));
+        }
+
+        [Test]
+        public void ToString_StringToString()
+        {
+            var map = new MapField<string, string> { { "foo", "bar" }, { "x", "y" } };
+            Assert.AreEqual("{ \"foo\": \"bar\", \"x\": \"y\" }", map.ToString());
+        }
+
+        [Test]
+        public void ToString_UnsupportedKeyType()
+        {
+            var map = new MapField<byte, string> { { 10, "foo" } };
+            Assert.Throws<ArgumentException>(() => map.ToString());
+        }
+
+        private static KeyValuePair<TKey, TValue> NewKeyValuePair<TKey, TValue>(TKey key, TValue value)
+        {
+            return new KeyValuePair<TKey, TValue>(key, value);
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
new file mode 100644
index 0000000..6852f75
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
@@ -0,0 +1,746 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using Google.Protobuf.TestProtos;
+using Google.Protobuf.WellKnownTypes;
+using NUnit.Framework;
+
+namespace Google.Protobuf.Collections
+{
+    public class RepeatedFieldTest
+    {
+        [Test]
+        public void NullValuesRejected()
+        {
+            var list = new RepeatedField<string>();
+            Assert.Throws<ArgumentNullException>(() => list.Add((string)null));
+            Assert.Throws<ArgumentNullException>(() => list.Add((IEnumerable<string>)null));
+            Assert.Throws<ArgumentNullException>(() => list.Add((RepeatedField<string>)null));
+            Assert.Throws<ArgumentNullException>(() => list.Contains(null));
+            Assert.Throws<ArgumentNullException>(() => list.IndexOf(null));
+        }
+
+        [Test]
+        public void Add_SingleItem()
+        {
+            var list = new RepeatedField<string>();
+            list.Add("foo");
+            Assert.AreEqual(1, list.Count);
+            Assert.AreEqual("foo", list[0]);
+        }
+
+        [Test]
+        public void Add_Sequence()
+        {
+            var list = new RepeatedField<string>();
+            list.Add(new[] { "foo", "bar" });
+            Assert.AreEqual(2, list.Count);
+            Assert.AreEqual("foo", list[0]);
+            Assert.AreEqual("bar", list[1]);
+        }
+
+        [Test]
+        public void AddRange_SlowPath()
+        {
+            var list = new RepeatedField<string>();
+            list.AddRange(new[] { "foo", "bar" }.Select(x => x));
+            Assert.AreEqual(2, list.Count);
+            Assert.AreEqual("foo", list[0]);
+            Assert.AreEqual("bar", list[1]);
+        }
+
+        [Test]
+        public void AddRange_SlowPath_NullsProhibited_ReferenceType()
+        {
+            var list = new RepeatedField<string>();
+            // It's okay for this to throw ArgumentNullException if necessary.
+            // It's not ideal, but not awful.
+            Assert.Catch<ArgumentException>(() => list.AddRange(new[] { "foo", null }.Select(x => x)));
+        }
+
+        [Test]
+        public void AddRange_SlowPath_NullsProhibited_NullableValueType()
+        {
+            var list = new RepeatedField<int?>();
+            // It's okay for this to throw ArgumentNullException if necessary.
+            // It's not ideal, but not awful.
+            Assert.Catch<ArgumentException>(() => list.AddRange(new[] { 20, (int?)null }.Select(x => x)));
+        }
+
+        [Test]
+        public void AddRange_Optimized_NonNullableValueType()
+        {
+            var list = new RepeatedField<int>();
+            list.AddRange(new List<int> { 20, 30 });
+            Assert.AreEqual(2, list.Count);
+            Assert.AreEqual(20, list[0]);
+            Assert.AreEqual(30, list[1]);
+        }
+
+        [Test]
+        public void AddRange_Optimized_ReferenceType()
+        {
+            var list = new RepeatedField<string>();
+            list.AddRange(new List<string> { "foo", "bar" });
+            Assert.AreEqual(2, list.Count);
+            Assert.AreEqual("foo", list[0]);
+            Assert.AreEqual("bar", list[1]);
+        }
+
+        [Test]
+        public void AddRange_Optimized_NullableValueType()
+        {
+            var list = new RepeatedField<int?>();
+            list.AddRange(new List<int?> { 20, 30 });
+            Assert.AreEqual(2, list.Count);
+            Assert.AreEqual((int?) 20, list[0]);
+            Assert.AreEqual((int?) 30, list[1]);
+        }
+
+        [Test]
+        public void AddRange_Optimized_NullsProhibited_ReferenceType()
+        {
+            // We don't just trust that a collection with a nullable element type doesn't contain nulls
+            var list = new RepeatedField<string>();
+            // It's okay for this to throw ArgumentNullException if necessary.
+            // It's not ideal, but not awful.
+            Assert.Catch<ArgumentException>(() => list.AddRange(new List<string> { "foo", null }));
+        }
+
+        [Test]
+        public void AddRange_Optimized_NullsProhibited_NullableValueType()
+        {
+            // We don't just trust that a collection with a nullable element type doesn't contain nulls
+            var list = new RepeatedField<int?>();
+            // It's okay for this to throw ArgumentNullException if necessary.
+            // It's not ideal, but not awful.
+            Assert.Catch<ArgumentException>(() => list.AddRange(new List<int?> { 20, null }));
+        }
+
+        [Test]
+        public void AddRange_AlreadyNotEmpty()
+        {
+            var list = new RepeatedField<int> { 1, 2, 3 };
+            list.AddRange(new List<int> { 4, 5, 6 });
+            CollectionAssert.AreEqual(new[] { 1, 2, 3, 4, 5, 6 }, list);
+        }
+
+        [Test]
+        public void AddRange_RepeatedField()
+        {
+            var list = new RepeatedField<string> { "original" };
+            list.AddRange(new RepeatedField<string> { "foo", "bar" });
+            Assert.AreEqual(3, list.Count);
+            Assert.AreEqual("original", list[0]);
+            Assert.AreEqual("foo", list[1]);
+            Assert.AreEqual("bar", list[2]);
+        }
+
+        [Test]
+        public void RemoveAt_Valid()
+        {
+            var list = new RepeatedField<string> { "first", "second", "third" };
+            list.RemoveAt(1);
+            CollectionAssert.AreEqual(new[] { "first", "third" }, list);
+            // Just check that these don't throw...
+            list.RemoveAt(list.Count - 1); // Now the count will be 1...
+            list.RemoveAt(0);
+            Assert.AreEqual(0, list.Count);
+        }
+
+        [Test]
+        public void RemoveAt_Invalid()
+        {
+            var list = new RepeatedField<string> { "first", "second", "third" };
+            Assert.Throws<ArgumentOutOfRangeException>(() => list.RemoveAt(-1));
+            Assert.Throws<ArgumentOutOfRangeException>(() => list.RemoveAt(3));
+        }
+
+        [Test]
+        public void Insert_Valid()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            list.Insert(1, "middle");
+            CollectionAssert.AreEqual(new[] { "first", "middle", "second" }, list);
+            list.Insert(3, "end");
+            CollectionAssert.AreEqual(new[] { "first", "middle", "second", "end" }, list);
+            list.Insert(0, "start");
+            CollectionAssert.AreEqual(new[] { "start", "first", "middle", "second", "end" }, list);
+        }
+
+        [Test]
+        public void Insert_Invalid()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            Assert.Throws<ArgumentOutOfRangeException>(() => list.Insert(-1, "foo"));
+            Assert.Throws<ArgumentOutOfRangeException>(() => list.Insert(3, "foo"));
+            Assert.Throws<ArgumentNullException>(() => list.Insert(0, null));
+        }
+
+        [Test]
+        public void Equals_RepeatedField()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            Assert.IsFalse(list.Equals((RepeatedField<string>) null));
+            Assert.IsTrue(list.Equals(list));
+            Assert.IsFalse(list.Equals(new RepeatedField<string> { "first", "third" }));
+            Assert.IsFalse(list.Equals(new RepeatedField<string> { "first" }));
+            Assert.IsTrue(list.Equals(new RepeatedField<string> { "first", "second" }));
+        }
+
+        [Test]
+        public void Equals_Object()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            Assert.IsFalse(list.Equals((object) null));
+            Assert.IsTrue(list.Equals((object) list));
+            Assert.IsFalse(list.Equals((object) new RepeatedField<string> { "first", "third" }));
+            Assert.IsFalse(list.Equals((object) new RepeatedField<string> { "first" }));
+            Assert.IsTrue(list.Equals((object) new RepeatedField<string> { "first", "second" }));
+            Assert.IsFalse(list.Equals(new object()));
+        }
+
+        [Test]
+        public void GetEnumerator_GenericInterface()
+        {
+            IEnumerable<string> list = new RepeatedField<string> { "first", "second" };
+            // Select gets rid of the optimizations in ToList...
+            CollectionAssert.AreEqual(new[] { "first", "second" }, list.Select(x => x).ToList());
+        }
+
+        [Test]
+        public void GetEnumerator_NonGenericInterface()
+        {
+            IEnumerable list = new RepeatedField<string> { "first", "second" };
+            CollectionAssert.AreEqual(new[] { "first", "second" }, list.Cast<object>().ToList());
+        }
+
+        [Test]
+        public void CopyTo()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            string[] stringArray = new string[4];
+            list.CopyTo(stringArray, 1);
+            CollectionAssert.AreEqual(new[] { null, "first", "second", null }, stringArray);
+        }
+
+        [Test]
+        public void Indexer_Get()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            Assert.AreEqual("first", list[0]);
+            Assert.AreEqual("second", list[1]);
+            Assert.Throws<ArgumentOutOfRangeException>(() => list[-1].GetHashCode());
+            Assert.Throws<ArgumentOutOfRangeException>(() => list[2].GetHashCode());
+        }
+
+        [Test]
+        public void Indexer_Set()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            list[0] = "changed";
+            Assert.AreEqual("changed", list[0]);
+            Assert.Throws<ArgumentNullException>(() => list[0] = null);
+            Assert.Throws<ArgumentOutOfRangeException>(() => list[-1] = "bad");
+            Assert.Throws<ArgumentOutOfRangeException>(() => list[2] = "bad");
+        }
+
+        [Test]
+        public void Clone_ReturnsMutable()
+        {
+            var list = new RepeatedField<int> { 0 };
+            var clone = list.Clone();
+            clone[0] = 1;
+        }
+
+        [Test]
+        public void Enumerator()
+        {
+            var list = new RepeatedField<string> { "first", "second" };
+            using (var enumerator = list.GetEnumerator())
+            {
+                Assert.IsTrue(enumerator.MoveNext());
+                Assert.AreEqual("first", enumerator.Current);
+                Assert.IsTrue(enumerator.MoveNext());
+                Assert.AreEqual("second", enumerator.Current);
+                Assert.IsFalse(enumerator.MoveNext());
+                Assert.IsFalse(enumerator.MoveNext());
+            }
+        }
+
+        [Test]
+        public void AddEntriesFrom_PackedInt32()
+        {
+            uint packedTag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            var length = CodedOutputStream.ComputeInt32Size(10)
+                + CodedOutputStream.ComputeInt32Size(999)
+                + CodedOutputStream.ComputeInt32Size(-1000);
+            output.WriteTag(packedTag);
+            output.WriteRawVarint32((uint) length);
+            output.WriteInt32(10);
+            output.WriteInt32(999);
+            output.WriteInt32(-1000);
+            output.Flush();
+            stream.Position = 0;
+
+            // Deliberately "expecting" a non-packed tag, but we detect that the data is
+            // actually packed.
+            uint nonPackedTag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var field = new RepeatedField<int>();
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(packedTag);
+            field.AddEntriesFrom(input, FieldCodec.ForInt32(nonPackedTag));
+            CollectionAssert.AreEqual(new[] { 10, 999, -1000 }, field);
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void AddEntriesFrom_NonPackedInt32()
+        {
+            uint nonPackedTag = WireFormat.MakeTag(10, WireFormat.WireType.Varint);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(nonPackedTag);
+            output.WriteInt32(10);
+            output.WriteTag(nonPackedTag);
+            output.WriteInt32(999);
+            output.WriteTag(nonPackedTag);
+            output.WriteInt32(-1000); // Just for variety...
+            output.Flush();
+            stream.Position = 0;
+
+            // Deliberately "expecting" a packed tag, but we detect that the data is
+            // actually not packed.
+            uint packedTag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var field = new RepeatedField<int>();
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(nonPackedTag);
+            field.AddEntriesFrom(input, FieldCodec.ForInt32(packedTag));
+            CollectionAssert.AreEqual(new[] { 10, 999, -1000 }, field);
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void AddEntriesFrom_String()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(tag);
+            output.WriteString("Foo");
+            output.WriteTag(tag);
+            output.WriteString("");
+            output.WriteTag(tag);
+            output.WriteString("Bar");
+            output.Flush();
+            stream.Position = 0;
+
+            var field = new RepeatedField<string>();
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(tag);
+            field.AddEntriesFrom(input, FieldCodec.ForString(tag));
+            CollectionAssert.AreEqual(new[] { "Foo", "", "Bar" }, field);
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void AddEntriesFrom_Message()
+        {
+            var message1 = new ForeignMessage { C = 2000 };
+            var message2 = new ForeignMessage { C = -250 };
+
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(tag);
+            output.WriteMessage(message1);
+            output.WriteTag(tag);
+            output.WriteMessage(message2);
+            output.Flush();
+            stream.Position = 0;
+
+            var field = new RepeatedField<ForeignMessage>();
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(tag);
+            field.AddEntriesFrom(input, FieldCodec.ForMessage(tag, ForeignMessage.Parser));
+            CollectionAssert.AreEqual(new[] { message1, message2}, field);
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void WriteTo_PackedInt32()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var field = new RepeatedField<int> { 10, 1000, 1000000 };
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            field.WriteTo(output, FieldCodec.ForInt32(tag));
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(tag);
+            var length = input.ReadLength();
+            Assert.AreEqual(10, input.ReadInt32());
+            Assert.AreEqual(1000, input.ReadInt32());
+            Assert.AreEqual(1000000, input.ReadInt32());
+            Assert.IsTrue(input.IsAtEnd);
+            Assert.AreEqual(1 + CodedOutputStream.ComputeLengthSize(length) + length, stream.Length);
+        }
+
+        [Test]
+        public void WriteTo_NonPackedInt32()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.Varint);
+            var field = new RepeatedField<int> { 10, 1000, 1000000};
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            field.WriteTo(output, FieldCodec.ForInt32(tag));
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(tag);
+            Assert.AreEqual(10, input.ReadInt32());
+            input.AssertNextTag(tag);
+            Assert.AreEqual(1000, input.ReadInt32());
+            input.AssertNextTag(tag);
+            Assert.AreEqual(1000000, input.ReadInt32());
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void WriteTo_String()
+        {
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var field = new RepeatedField<string> { "Foo", "", "Bar" };
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            field.WriteTo(output, FieldCodec.ForString(tag));
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(tag);
+            Assert.AreEqual("Foo", input.ReadString());
+            input.AssertNextTag(tag);
+            Assert.AreEqual("", input.ReadString());
+            input.AssertNextTag(tag);
+            Assert.AreEqual("Bar", input.ReadString());
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void WriteTo_Message()
+        {
+            var message1 = new ForeignMessage { C = 20 };
+            var message2 = new ForeignMessage { C = 25 };
+            uint tag = WireFormat.MakeTag(10, WireFormat.WireType.LengthDelimited);
+            var field = new RepeatedField<ForeignMessage> { message1, message2 };
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            field.WriteTo(output, FieldCodec.ForMessage(tag, ForeignMessage.Parser));
+            output.Flush();
+            stream.Position = 0;
+
+            var input = new CodedInputStream(stream);
+            input.AssertNextTag(tag);
+            Assert.AreEqual(message1, input.ReadMessage(ForeignMessage.Parser));
+            input.AssertNextTag(tag);
+            Assert.AreEqual(message2, input.ReadMessage(ForeignMessage.Parser));
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        [Test]
+        public void CalculateSize_VariableSizeNonPacked()
+        {
+            var list = new RepeatedField<int> { 1, 500, 1 };
+            var tag = WireFormat.MakeTag(1, WireFormat.WireType.Varint);
+            // 2 bytes for the first entry, 3 bytes for the second, 2 bytes for the third
+            Assert.AreEqual(7, list.CalculateSize(FieldCodec.ForInt32(tag)));
+        }
+
+        [Test]
+        public void CalculateSize_FixedSizeNonPacked()
+        {
+            var list = new RepeatedField<int> { 1, 500, 1 };
+            var tag = WireFormat.MakeTag(1, WireFormat.WireType.Fixed32);
+            // 5 bytes for the each entry
+            Assert.AreEqual(15, list.CalculateSize(FieldCodec.ForSFixed32(tag)));
+        }
+
+        [Test]
+        public void CalculateSize_VariableSizePacked()
+        {
+            var list = new RepeatedField<int> { 1, 500, 1};
+            var tag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+            // 1 byte for the tag, 1 byte for the length,
+            // 1 byte for the first entry, 2 bytes for the second, 1 byte for the third
+            Assert.AreEqual(6, list.CalculateSize(FieldCodec.ForInt32(tag)));
+        }
+
+        [Test]
+        public void CalculateSize_FixedSizePacked()
+        {
+            var list = new RepeatedField<int> { 1, 500, 1 };
+            var tag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+            // 1 byte for the tag, 1 byte for the length, 4 bytes per entry
+            Assert.AreEqual(14, list.CalculateSize(FieldCodec.ForSFixed32(tag)));
+        }
+
+        [Test]
+        public void TestNegativeEnumArray()
+        {
+            int arraySize = 1 + 1 + (11 * 5);
+            int msgSize = arraySize;
+            byte[] bytes = new byte[msgSize];
+            CodedOutputStream output = new CodedOutputStream(bytes);
+            uint tag = WireFormat.MakeTag(8, WireFormat.WireType.Varint);
+            for (int i = 0; i >= -5; i--)
+            {
+                output.WriteTag(tag);
+                output.WriteEnum(i);
+            }
+
+            Assert.AreEqual(0, output.SpaceLeft);
+
+            CodedInputStream input = new CodedInputStream(bytes);
+            tag = input.ReadTag();
+
+            RepeatedField<SampleEnum> values = new RepeatedField<SampleEnum>();
+            values.AddEntriesFrom(input, FieldCodec.ForEnum(tag, x => (int)x, x => (SampleEnum)x));
+
+            Assert.AreEqual(6, values.Count);
+            Assert.AreEqual(SampleEnum.None, values[0]);
+            Assert.AreEqual(((SampleEnum)(-1)), values[1]);
+            Assert.AreEqual(SampleEnum.NegativeValue, values[2]);
+            Assert.AreEqual(((SampleEnum)(-3)), values[3]);
+            Assert.AreEqual(((SampleEnum)(-4)), values[4]);
+            Assert.AreEqual(((SampleEnum)(-5)), values[5]);
+        }
+
+
+        [Test]
+        public void TestNegativeEnumPackedArray()
+        {
+            int arraySize = 1 + (10 * 5);
+            int msgSize = 1 + 1 + arraySize;
+            byte[] bytes = new byte[msgSize];
+            CodedOutputStream output = new CodedOutputStream(bytes);
+            // Length-delimited to show we want the packed representation
+            uint tag = WireFormat.MakeTag(8, WireFormat.WireType.LengthDelimited);
+            output.WriteTag(tag);
+            int size = 0;
+            for (int i = 0; i >= -5; i--)
+            {
+                size += CodedOutputStream.ComputeEnumSize(i);
+            }
+            output.WriteRawVarint32((uint)size);
+            for (int i = 0; i >= -5; i--)
+            {
+                output.WriteEnum(i);
+            }
+            Assert.AreEqual(0, output.SpaceLeft);
+
+            CodedInputStream input = new CodedInputStream(bytes);
+            tag = input.ReadTag();
+
+            RepeatedField<SampleEnum> values = new RepeatedField<SampleEnum>();
+            values.AddEntriesFrom(input, FieldCodec.ForEnum(tag, x => (int)x, x => (SampleEnum)x));
+
+            Assert.AreEqual(6, values.Count);
+            Assert.AreEqual(SampleEnum.None, values[0]);
+            Assert.AreEqual(((SampleEnum)(-1)), values[1]);
+            Assert.AreEqual(SampleEnum.NegativeValue, values[2]);
+            Assert.AreEqual(((SampleEnum)(-3)), values[3]);
+            Assert.AreEqual(((SampleEnum)(-4)), values[4]);
+            Assert.AreEqual(((SampleEnum)(-5)), values[5]);
+        }
+
+        // Fairly perfunctory tests for the non-generic IList implementation
+        [Test]
+        public void IList_Indexer()
+        {
+            var field = new RepeatedField<string> { "first", "second" };
+            IList list = field;
+            Assert.AreEqual("first", list[0]);
+            list[1] = "changed";
+            Assert.AreEqual("changed", field[1]);
+        }
+
+        [Test]
+        public void IList_Contains()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            Assert.IsTrue(list.Contains("second"));
+            Assert.IsFalse(list.Contains("third"));
+            Assert.IsFalse(list.Contains(new object()));
+        }
+
+        [Test]
+        public void IList_Add()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            list.Add("third");
+            CollectionAssert.AreEqual(new[] { "first", "second", "third" }, list);
+        }
+
+        [Test]
+        public void IList_Remove()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            list.Remove("third"); // No-op, no exception
+            list.Remove(new object()); // No-op, no exception
+            list.Remove("first");
+            CollectionAssert.AreEqual(new[] { "second" }, list);
+        }
+
+        [Test]
+        public void IList_IsFixedSize()
+        {
+            var field = new RepeatedField<string> { "first", "second" };
+            IList list = field;
+            Assert.IsFalse(list.IsFixedSize);
+        }
+
+        [Test]
+        public void IList_IndexOf()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            Assert.AreEqual(1, list.IndexOf("second"));
+            Assert.AreEqual(-1, list.IndexOf("third"));
+            Assert.AreEqual(-1, list.IndexOf(new object()));
+        }
+
+        [Test]
+        public void IList_SyncRoot()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            Assert.AreSame(list, list.SyncRoot);
+        }
+
+        [Test]
+        public void IList_CopyTo()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            string[] stringArray = new string[4];
+            list.CopyTo(stringArray, 1);
+            CollectionAssert.AreEqual(new[] { null, "first",  "second", null }, stringArray);
+
+            object[] objectArray = new object[4];
+            list.CopyTo(objectArray, 1);
+            CollectionAssert.AreEqual(new[] { null, "first", "second", null }, objectArray);
+
+            Assert.Throws<ArrayTypeMismatchException>(() => list.CopyTo(new StringBuilder[4], 1));
+            Assert.Throws<ArrayTypeMismatchException>(() => list.CopyTo(new int[4], 1));
+        }
+
+        [Test]
+        public void IList_IsSynchronized()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            Assert.IsFalse(list.IsSynchronized);
+        }
+
+        [Test]
+        public void IList_Insert()
+        {
+            IList list = new RepeatedField<string> { "first", "second" };
+            list.Insert(1, "middle");
+            CollectionAssert.AreEqual(new[] { "first", "middle", "second" }, list);
+        }
+
+        [Test]
+        public void ToString_Integers()
+        {
+            var list = new RepeatedField<int> { 5, 10, 20 };
+            var text = list.ToString();
+            Assert.AreEqual("[ 5, 10, 20 ]", text);
+        }
+
+        [Test]
+        public void ToString_Strings()
+        {
+            var list = new RepeatedField<string> { "x", "y", "z" };
+            var text = list.ToString();
+            Assert.AreEqual("[ \"x\", \"y\", \"z\" ]", text);
+        }
+
+        [Test]
+        public void ToString_Messages()
+        {
+            var list = new RepeatedField<TestAllTypes> { new TestAllTypes { SingleDouble = 1.5 }, new TestAllTypes { SingleInt32 = 10 } };
+            var text = list.ToString();
+            Assert.AreEqual("[ { \"singleDouble\": 1.5 }, { \"singleInt32\": 10 } ]", text);
+        }
+
+        [Test]
+        public void ToString_Empty()
+        {
+            var list = new RepeatedField<TestAllTypes> { };
+            var text = list.ToString();
+            Assert.AreEqual("[ ]", text);
+        }
+
+        [Test]
+        public void ToString_InvalidElementType()
+        {
+            var list = new RepeatedField<decimal> { 15m };
+            Assert.Throws<ArgumentException>(() => list.ToString());
+        }
+
+        [Test]
+        public void ToString_Timestamp()
+        {
+            var list = new RepeatedField<Timestamp> { Timestamp.FromDateTime(new DateTime(2015, 10, 1, 12, 34, 56, DateTimeKind.Utc)) };
+            var text = list.ToString();
+            Assert.AreEqual("[ \"2015-10-01T12:34:56Z\" ]", text);
+        }
+
+        [Test]
+        public void ToString_Struct()
+        {
+            var message = new Struct { Fields = { { "foo", new Value { NumberValue = 20 } } } };
+            var list = new RepeatedField<Struct> { message };
+            var text = list.ToString();
+            Assert.AreEqual(text, "[ { \"foo\": 20 } ]", message.ToString());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Compatibility/PropertyInfoExtensionsTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Compatibility/PropertyInfoExtensionsTest.cs
new file mode 100644
index 0000000..df23a09
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Compatibility/PropertyInfoExtensionsTest.cs
@@ -0,0 +1,98 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using NUnit.Framework;
+using System.Reflection;
+
+namespace Google.Protobuf.Compatibility
+{
+    public class PropertyInfoExtensionsTest
+    {
+        public string PublicReadWrite { get; set; }
+        private string PrivateReadWrite { get; set; }
+        public string PublicReadPrivateWrite { get; private set; }
+        public string PrivateReadPublicWrite { private get; set; }
+        public string PublicReadOnly { get { return null; } }
+        private string PrivateReadOnly { get { return null; } }
+        public string PublicWriteOnly { set { } }
+        private string PrivateWriteOnly { set {  } }
+
+        [Test]
+        [TestCase("PublicReadWrite")]
+        [TestCase("PublicReadPrivateWrite")]
+        [TestCase("PublicReadOnly")]
+        public void GetGetMethod_Success(string name)
+        {
+            var propertyInfo = typeof(PropertyInfoExtensionsTest)
+                .GetProperty(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
+            Assert.IsNotNull(PropertyInfoExtensions.GetGetMethod(propertyInfo));
+        }
+
+        [Test]
+        [TestCase("PrivateReadWrite")]
+        [TestCase("PrivateReadPublicWrite")]
+        [TestCase("PrivateReadOnly")]
+        [TestCase("PublicWriteOnly")]
+        [TestCase("PrivateWriteOnly")]
+        public void GetGetMethod_NoAccessibleGetter(string name)
+        {
+            var propertyInfo = typeof(PropertyInfoExtensionsTest)
+                .GetProperty(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
+            Assert.IsNull(PropertyInfoExtensions.GetGetMethod(propertyInfo));
+        }
+
+        [Test]
+        [TestCase("PublicReadWrite")]
+        [TestCase("PrivateReadPublicWrite")]
+        [TestCase("PublicWriteOnly")]
+        public void GetSetMethod_Success(string name)
+        {
+            var propertyInfo = typeof(PropertyInfoExtensionsTest)
+                .GetProperty(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
+            Assert.IsNotNull(PropertyInfoExtensions.GetSetMethod(propertyInfo));
+        }
+
+        [Test]
+        [TestCase("PublicReadPrivateWrite")]
+        [TestCase("PrivateReadWrite")]
+        [TestCase("PrivateReadOnly")]
+        [TestCase("PublicReadOnly")]
+        [TestCase("PrivateWriteOnly")]
+        public void GetSetMethod_NoAccessibleGetter(string name)
+        {
+            var propertyInfo = typeof(PropertyInfoExtensionsTest)
+                .GetProperty(name, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
+            Assert.IsNull(PropertyInfoExtensions.GetSetMethod(propertyInfo));
+        }
+    }
+
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Compatibility/TypeExtensionsTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Compatibility/TypeExtensionsTest.cs
new file mode 100644
index 0000000..f430b06
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Compatibility/TypeExtensionsTest.cs
@@ -0,0 +1,117 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+using NUnit.Framework;
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+
+#if !DOTNET35
+namespace Google.Protobuf.Compatibility
+{
+    public class TypeExtensionsTest
+    {
+        public class DerivedList : List<string> { }
+        public string PublicProperty { get; set; }
+        private string PrivateProperty { get; set; }
+
+        public void PublicMethod()
+        {
+        }
+
+        private void PrivateMethod()
+        {
+        }
+
+        [Test]
+        [TestCase(typeof(object), typeof(string), true)]
+        [TestCase(typeof(object), typeof(int), true)]
+        [TestCase(typeof(string), typeof(string), true)]
+        [TestCase(typeof(string), typeof(object), false)]
+        [TestCase(typeof(string), typeof(int), false)]
+        [TestCase(typeof(int), typeof(int), true)]
+        [TestCase(typeof(ValueType), typeof(int), true)]
+        [TestCase(typeof(long), typeof(int), false)] // 
+        public void IsAssignableFrom(Type target, Type argument, bool expected)
+        {
+            Assert.AreEqual(expected, TypeExtensions.IsAssignableFrom(target, argument));
+        }
+
+        [Test]
+        [TestCase(typeof(DerivedList), "Count")] // Go up the type hierarchy
+        [TestCase(typeof(List<string>), "Count")]
+        [TestCase(typeof(List<>), "Count")]
+        [TestCase(typeof(TypeExtensionsTest), "PublicProperty")]
+        public void GetProperty_Success(Type type, string name)
+        {
+            var property = TypeExtensions.GetProperty(type, name);
+            Assert.IsNotNull(property);
+            Assert.AreEqual(name, property.Name);
+        }
+
+        [Test]
+        [TestCase(typeof(TypeExtensionsTest), "PrivateProperty")]
+        [TestCase(typeof(TypeExtensionsTest), "Garbage")]
+        public void GetProperty_NoSuchProperty(Type type, string name)
+        {
+            var property = TypeExtensions.GetProperty(type, name);
+            Assert.IsNull(property);
+        }
+
+        [Test]
+        [TestCase(typeof(DerivedList), "RemoveAt")] // Go up the type hierarchy
+        [TestCase(typeof(List<>), "RemoveAt")]
+        [TestCase(typeof(TypeExtensionsTest), "PublicMethod")]
+        public void GetMethod_Success(Type type, string name)
+        {
+            var method = TypeExtensions.GetMethod(type, name);
+            Assert.IsNotNull(method);
+            Assert.AreEqual(name, method.Name);
+        }
+
+        [Test]
+        [TestCase(typeof(TypeExtensionsTest), "PrivateMethod")]
+        [TestCase(typeof(TypeExtensionsTest), "GarbageMethod")]
+        public void GetMethod_NoSuchMethod(Type type, string name)
+        {
+            var method = TypeExtensions.GetMethod(type, name);
+            Assert.IsNull(method);
+        }
+
+        [Test]
+        [TestCase(typeof(List<string>), "IndexOf")]
+        public void GetMethod_Ambiguous(Type type, string name)
+        {
+            Assert.Throws<AmbiguousMatchException>(() => TypeExtensions.GetMethod(type, name));
+        }
+    }
+}
+#endif
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/DeprecatedMemberTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/DeprecatedMemberTest.cs
new file mode 100644
index 0000000..34d5b9f
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/DeprecatedMemberTest.cs
@@ -0,0 +1,55 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+    
+using System;
+using System.Reflection;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class DeprecatedMemberTest
+    {
+        private static void AssertIsDeprecated(MemberInfo member)
+        {
+            Assert.NotNull(member);
+            Assert.IsTrue(member.IsDefined(typeof(ObsoleteAttribute), false), "Member not obsolete: " + member);
+        }
+
+        [Test]
+        public void TestDepreatedPrimitiveValue()
+        {
+            AssertIsDeprecated(typeof(TestDeprecatedFields).GetProperty("DeprecatedInt32"));
+        }
+
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/EqualityTester.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/EqualityTester.cs
new file mode 100644
index 0000000..a669bab
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/EqualityTester.cs
@@ -0,0 +1,64 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Helper methods when testing equality. NUnit's Assert.AreEqual and
+    /// Assert.AreNotEqual methods try to be clever with collections, which can
+    /// be annoying...
+    /// </summary>
+    internal static class EqualityTester
+    {
+        public static void AssertEquality<T>(T first, T second) where T : IEquatable<T>
+        {
+            Assert.IsTrue(first.Equals(second));
+            Assert.IsTrue(first.Equals((object) second));
+            Assert.AreEqual(first.GetHashCode(), second.GetHashCode());
+        }
+
+        public static void AssertInequality<T>(T first, T second) where T : IEquatable<T>
+        {
+            Assert.IsFalse(first.Equals(second));
+            Assert.IsFalse(first.Equals((object) second));
+            // While this isn't a requirement, the chances of this test failing due to
+            // coincidence rather than a bug are very small.
+            if (first != null && second != null)
+            {
+                Assert.AreNotEqual(first.GetHashCode(), second.GetHashCode());
+            }
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/FieldCodecTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/FieldCodecTest.cs
new file mode 100644
index 0000000..0e2bad5
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/FieldCodecTest.cs
@@ -0,0 +1,196 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class FieldCodecTest
+    {
+#pragma warning disable 0414 // Used by tests via reflection - do not remove!
+        private static readonly List<ICodecTestData> Codecs = new List<ICodecTestData>
+        {
+            new FieldCodecTestData<bool>(FieldCodec.ForBool(100), true, "Bool"),
+            new FieldCodecTestData<string>(FieldCodec.ForString(100), "sample", "String"),
+            new FieldCodecTestData<ByteString>(FieldCodec.ForBytes(100), ByteString.CopyFrom(1, 2, 3), "Bytes"),
+            new FieldCodecTestData<int>(FieldCodec.ForInt32(100), -1000, "Int32"),
+            new FieldCodecTestData<int>(FieldCodec.ForSInt32(100), -1000, "SInt32"),
+            new FieldCodecTestData<int>(FieldCodec.ForSFixed32(100), -1000, "SFixed32"),
+            new FieldCodecTestData<uint>(FieldCodec.ForUInt32(100), 1234, "UInt32"),
+            new FieldCodecTestData<uint>(FieldCodec.ForFixed32(100), 1234, "Fixed32"),
+            new FieldCodecTestData<long>(FieldCodec.ForInt64(100), -1000, "Int64"),
+            new FieldCodecTestData<long>(FieldCodec.ForSInt64(100), -1000, "SInt64"),
+            new FieldCodecTestData<long>(FieldCodec.ForSFixed64(100), -1000, "SFixed64"),
+            new FieldCodecTestData<ulong>(FieldCodec.ForUInt64(100), 1234, "UInt64"),
+            new FieldCodecTestData<ulong>(FieldCodec.ForFixed64(100), 1234, "Fixed64"),
+            new FieldCodecTestData<float>(FieldCodec.ForFloat(100), 1234.5f, "Float"),
+            new FieldCodecTestData<double>(FieldCodec.ForDouble(100), 1234567890.5d, "Double"),
+            new FieldCodecTestData<ForeignEnum>(
+                FieldCodec.ForEnum(100, t => (int) t, t => (ForeignEnum) t), ForeignEnum.ForeignBaz, "Enum"),
+            new FieldCodecTestData<ForeignMessage>(
+                FieldCodec.ForMessage(100, ForeignMessage.Parser), new ForeignMessage { C = 10 }, "Message"),
+        };
+#pragma warning restore 0414
+
+        [Test, TestCaseSource("Codecs")]
+        public void RoundTripWithTag(ICodecTestData codec)
+        {
+            codec.TestRoundTripWithTag();
+        }
+
+        [Test, TestCaseSource("Codecs")]
+        public void RoundTripRaw(ICodecTestData codec)
+        {
+            codec.TestRoundTripRaw();
+        }
+
+        [Test, TestCaseSource("Codecs")]
+        public void CalculateSize(ICodecTestData codec)
+        {
+            codec.TestCalculateSizeWithTag();
+        }
+
+        [Test, TestCaseSource("Codecs")]
+        public void DefaultValue(ICodecTestData codec)
+        {
+            codec.TestDefaultValue();
+        }
+
+        [Test, TestCaseSource("Codecs")]
+        public void FixedSize(ICodecTestData codec)
+        {
+            codec.TestFixedSize();
+        }
+
+        // This is ugly, but it means we can have a non-generic interface.
+        // It feels like NUnit should support this better, but I don't know
+        // of any better ways right now.
+        public interface ICodecTestData
+        {
+            void TestRoundTripRaw();
+            void TestRoundTripWithTag();
+            void TestCalculateSizeWithTag();
+            void TestDefaultValue();
+            void TestFixedSize();
+        }
+
+        public class FieldCodecTestData<T> : ICodecTestData
+        {
+            private readonly FieldCodec<T> codec;
+            private readonly T sampleValue;
+            private readonly string name;
+
+            public FieldCodecTestData(FieldCodec<T> codec, T sampleValue, string name)
+            {
+                this.codec = codec;
+                this.sampleValue = sampleValue;
+                this.name = name;
+            }
+
+            public void TestRoundTripRaw()
+            {
+                var stream = new MemoryStream();
+                var codedOutput = new CodedOutputStream(stream);
+                codec.ValueWriter(codedOutput, sampleValue);
+                codedOutput.Flush();
+                stream.Position = 0;
+                var codedInput = new CodedInputStream(stream);
+                Assert.AreEqual(sampleValue, codec.ValueReader(codedInput));
+                Assert.IsTrue(codedInput.IsAtEnd);
+            }
+
+            public void TestRoundTripWithTag()
+            {
+                var stream = new MemoryStream();
+                var codedOutput = new CodedOutputStream(stream);
+                codec.WriteTagAndValue(codedOutput, sampleValue);
+                codedOutput.Flush();
+                stream.Position = 0;
+                var codedInput = new CodedInputStream(stream);
+                codedInput.AssertNextTag(codec.Tag);
+                Assert.AreEqual(sampleValue, codec.Read(codedInput));
+                Assert.IsTrue(codedInput.IsAtEnd);
+            }
+
+            public void TestCalculateSizeWithTag()
+            {
+                var stream = new MemoryStream();
+                var codedOutput = new CodedOutputStream(stream);
+                codec.WriteTagAndValue(codedOutput, sampleValue);
+                codedOutput.Flush();
+                Assert.AreEqual(stream.Position, codec.CalculateSizeWithTag(sampleValue));
+            }
+
+            public void TestDefaultValue()
+            {
+                // WriteTagAndValue ignores default values
+                var stream = new MemoryStream();
+                var codedOutput = new CodedOutputStream(stream);
+                codec.WriteTagAndValue(codedOutput, codec.DefaultValue);
+                codedOutput.Flush();
+                Assert.AreEqual(0, stream.Position);
+                Assert.AreEqual(0, codec.CalculateSizeWithTag(codec.DefaultValue));
+                if (typeof(T).GetTypeInfo().IsValueType)
+                {
+                    Assert.AreEqual(default(T), codec.DefaultValue);
+                }
+
+                // The plain ValueWriter/ValueReader delegates don't.
+                if (codec.DefaultValue != null) // This part isn't appropriate for message types.
+                {
+                    codedOutput = new CodedOutputStream(stream);
+                    codec.ValueWriter(codedOutput, codec.DefaultValue);
+                    codedOutput.Flush();
+                    Assert.AreNotEqual(0, stream.Position);
+                    Assert.AreEqual(stream.Position, codec.ValueSizeCalculator(codec.DefaultValue));
+                    stream.Position = 0;
+                    var codedInput = new CodedInputStream(stream);
+                    Assert.AreEqual(codec.DefaultValue, codec.ValueReader(codedInput));
+                }
+            }
+
+            public void TestFixedSize()
+            {
+                Assert.AreEqual(name.Contains("Fixed"), codec.FixedSize != 0);
+            }
+
+            public override string ToString()
+            {
+                return name;
+            }
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/GeneratedMessageTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/GeneratedMessageTest.cs
new file mode 100644
index 0000000..429c51f
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/GeneratedMessageTest.cs
@@ -0,0 +1,725 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.IO;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using Google.Protobuf.WellKnownTypes;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Tests around the generated TestAllTypes message.
+    /// </summary>
+    public class GeneratedMessageTest
+    {
+        [Test]
+        public void EmptyMessageFieldDistinctFromMissingMessageField()
+        {
+            // This demonstrates what we're really interested in...
+            var message1 = new TestAllTypes { SingleForeignMessage = new ForeignMessage() };
+            var message2 = new TestAllTypes(); // SingleForeignMessage is null
+            EqualityTester.AssertInequality(message1, message2);
+        }
+
+        [Test]
+        public void DefaultValues()
+        {
+            // Single fields
+            var message = new TestAllTypes();
+            Assert.AreEqual(false, message.SingleBool);
+            Assert.AreEqual(ByteString.Empty, message.SingleBytes);
+            Assert.AreEqual(0.0, message.SingleDouble);
+            Assert.AreEqual(0, message.SingleFixed32);
+            Assert.AreEqual(0L, message.SingleFixed64);
+            Assert.AreEqual(0.0f, message.SingleFloat);
+            Assert.AreEqual(ForeignEnum.ForeignUnspecified, message.SingleForeignEnum);
+            Assert.IsNull(message.SingleForeignMessage);
+            Assert.AreEqual(ImportEnum.Unspecified, message.SingleImportEnum);
+            Assert.IsNull(message.SingleImportMessage);
+            Assert.AreEqual(0, message.SingleInt32);
+            Assert.AreEqual(0L, message.SingleInt64);
+            Assert.AreEqual(TestAllTypes.Types.NestedEnum.Unspecified, message.SingleNestedEnum);
+            Assert.IsNull(message.SingleNestedMessage);
+            Assert.IsNull(message.SinglePublicImportMessage);
+            Assert.AreEqual(0, message.SingleSfixed32);
+            Assert.AreEqual(0L, message.SingleSfixed64);
+            Assert.AreEqual(0, message.SingleSint32);
+            Assert.AreEqual(0L, message.SingleSint64);
+            Assert.AreEqual("", message.SingleString);
+            Assert.AreEqual(0U, message.SingleUint32);
+            Assert.AreEqual(0UL, message.SingleUint64);
+
+            // Repeated fields
+            Assert.AreEqual(0, message.RepeatedBool.Count);
+            Assert.AreEqual(0, message.RepeatedBytes.Count);
+            Assert.AreEqual(0, message.RepeatedDouble.Count);
+            Assert.AreEqual(0, message.RepeatedFixed32.Count);
+            Assert.AreEqual(0, message.RepeatedFixed64.Count);
+            Assert.AreEqual(0, message.RepeatedFloat.Count);
+            Assert.AreEqual(0, message.RepeatedForeignEnum.Count);
+            Assert.AreEqual(0, message.RepeatedForeignMessage.Count);
+            Assert.AreEqual(0, message.RepeatedImportEnum.Count);
+            Assert.AreEqual(0, message.RepeatedImportMessage.Count);
+            Assert.AreEqual(0, message.RepeatedNestedEnum.Count);
+            Assert.AreEqual(0, message.RepeatedNestedMessage.Count);
+            Assert.AreEqual(0, message.RepeatedPublicImportMessage.Count);
+            Assert.AreEqual(0, message.RepeatedSfixed32.Count);
+            Assert.AreEqual(0, message.RepeatedSfixed64.Count);
+            Assert.AreEqual(0, message.RepeatedSint32.Count);
+            Assert.AreEqual(0, message.RepeatedSint64.Count);
+            Assert.AreEqual(0, message.RepeatedString.Count);
+            Assert.AreEqual(0, message.RepeatedUint32.Count);
+            Assert.AreEqual(0, message.RepeatedUint64.Count);
+
+            // Oneof fields
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.None, message.OneofFieldCase);
+            Assert.AreEqual(0, message.OneofUint32);
+            Assert.AreEqual("", message.OneofString);
+            Assert.AreEqual(ByteString.Empty, message.OneofBytes);
+            Assert.IsNull(message.OneofNestedMessage);
+        }
+
+        [Test]
+        public void NullStringAndBytesRejected()
+        {
+            var message = new TestAllTypes();
+            Assert.Throws<ArgumentNullException>(() => message.SingleString = null);
+            Assert.Throws<ArgumentNullException>(() => message.OneofString = null);
+            Assert.Throws<ArgumentNullException>(() => message.SingleBytes = null);
+            Assert.Throws<ArgumentNullException>(() => message.OneofBytes = null);
+        }
+
+        [Test]
+        public void RoundTrip_Empty()
+        {
+            var message = new TestAllTypes();
+            // Without setting any values, there's nothing to write.
+            byte[] bytes = message.ToByteArray();
+            Assert.AreEqual(0, bytes.Length);
+            TestAllTypes parsed = TestAllTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void RoundTrip_SingleValues()
+        {
+            var message = new TestAllTypes
+            {
+                SingleBool = true,
+                SingleBytes = ByteString.CopyFrom(1, 2, 3, 4),
+                SingleDouble = 23.5,
+                SingleFixed32 = 23,
+                SingleFixed64 = 1234567890123,
+                SingleFloat = 12.25f,
+                SingleForeignEnum = ForeignEnum.ForeignBar,
+                SingleForeignMessage = new ForeignMessage { C = 10 },
+                SingleImportEnum = ImportEnum.ImportBaz,
+                SingleImportMessage = new ImportMessage { D = 20 },
+                SingleInt32 = 100,
+                SingleInt64 = 3210987654321,
+                SingleNestedEnum = TestAllTypes.Types.NestedEnum.Foo,
+                SingleNestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 35 },
+                SinglePublicImportMessage = new PublicImportMessage { E = 54 },
+                SingleSfixed32 = -123,
+                SingleSfixed64 = -12345678901234,
+                SingleSint32 = -456,
+                SingleSint64 = -12345678901235,
+                SingleString = "test",
+                SingleUint32 = uint.MaxValue,
+                SingleUint64 = ulong.MaxValue
+            };
+
+            byte[] bytes = message.ToByteArray();
+            TestAllTypes parsed = TestAllTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void RoundTrip_RepeatedValues()
+        {
+            var message = new TestAllTypes
+            {
+                RepeatedBool = { true, false },
+                RepeatedBytes = { ByteString.CopyFrom(1, 2, 3, 4), ByteString.CopyFrom(5, 6) },
+                RepeatedDouble = { -12.25, 23.5 },
+                RepeatedFixed32 = { uint.MaxValue, 23 },
+                RepeatedFixed64 = { ulong.MaxValue, 1234567890123 },
+                RepeatedFloat = { 100f, 12.25f },
+                RepeatedForeignEnum = { ForeignEnum.ForeignFoo, ForeignEnum.ForeignBar },
+                RepeatedForeignMessage = { new ForeignMessage(), new ForeignMessage { C = 10 } },
+                RepeatedImportEnum = { ImportEnum.ImportBaz, ImportEnum.Unspecified },
+                RepeatedImportMessage = { new ImportMessage { D = 20 }, new ImportMessage { D = 25 } },
+                RepeatedInt32 = { 100, 200 },
+                RepeatedInt64 = { 3210987654321, long.MaxValue },
+                RepeatedNestedEnum = { TestAllTypes.Types.NestedEnum.Foo, TestAllTypes.Types.NestedEnum.Neg },
+                RepeatedNestedMessage = { new TestAllTypes.Types.NestedMessage { Bb = 35 }, new TestAllTypes.Types.NestedMessage { Bb = 10 } },
+                RepeatedPublicImportMessage = { new PublicImportMessage { E = 54 }, new PublicImportMessage { E = -1 } },
+                RepeatedSfixed32 = { -123, 123 },
+                RepeatedSfixed64 = { -12345678901234, 12345678901234 },
+                RepeatedSint32 = { -456, 100 },
+                RepeatedSint64 = { -12345678901235, 123 },
+                RepeatedString = { "foo", "bar" },
+                RepeatedUint32 = { uint.MaxValue, uint.MinValue },
+                RepeatedUint64 = { ulong.MaxValue, uint.MinValue }
+            };
+
+            byte[] bytes = message.ToByteArray();
+            TestAllTypes parsed = TestAllTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+        }
+
+        // Note that not every map within map_unittest_proto3 is used. They all go through very
+        // similar code paths. The fact that all maps are present is validation that we have codecs
+        // for every type.
+        [Test]
+        public void RoundTrip_Maps()
+        {
+            var message = new TestMap
+            {
+                MapBoolBool = {
+                    { false, true },
+                    { true, false }
+                },
+                MapInt32Bytes = {
+                    { 5, ByteString.CopyFrom(6, 7, 8) },
+                    { 25, ByteString.CopyFrom(1, 2, 3, 4, 5) },
+                    { 10, ByteString.Empty }
+                },
+                MapInt32ForeignMessage = {
+                    { 0, new ForeignMessage { C = 10 } },
+                    { 5, new ForeignMessage() },
+                },
+                MapInt32Enum = {
+                    { 1, MapEnum.Bar },
+                    { 2000, MapEnum.Foo }
+                }
+            };
+
+            byte[] bytes = message.ToByteArray();
+            TestMap parsed = TestMap.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void MapWithEmptyEntry()
+        {
+            var message = new TestMap
+            {
+                MapInt32Bytes = { { 0, ByteString.Empty } }
+            };
+
+            byte[] bytes = message.ToByteArray();
+            Assert.AreEqual(2, bytes.Length); // Tag for field entry (1 byte), length of entry (0; 1 byte)
+
+            var parsed = TestMap.Parser.ParseFrom(bytes);
+            Assert.AreEqual(1, parsed.MapInt32Bytes.Count);
+            Assert.AreEqual(ByteString.Empty, parsed.MapInt32Bytes[0]);
+        }
+
+        [Test]
+        public void MapWithOnlyValue()
+        {
+            // Hand-craft the stream to contain a single entry with just a value.
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+            output.WriteTag(TestMap.MapInt32ForeignMessageFieldNumber, WireFormat.WireType.LengthDelimited);
+            var nestedMessage = new ForeignMessage { C = 20 };
+            // Size of the entry (tag, size written by WriteMessage, data written by WriteMessage)
+            output.WriteLength(2 + nestedMessage.CalculateSize());
+            output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+            output.WriteMessage(nestedMessage);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(nestedMessage, parsed.MapInt32ForeignMessage[0]);
+        }
+
+        [Test]
+        public void MapWithOnlyKey_PrimitiveValue()
+        {
+            // Hand-craft the stream to contain a single entry with just a key.
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+            output.WriteTag(TestMap.MapInt32DoubleFieldNumber, WireFormat.WireType.LengthDelimited);
+            int key = 10;
+            output.WriteLength(1 + CodedOutputStream.ComputeInt32Size(key));
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(0.0, parsed.MapInt32Double[key]);
+        }
+
+        [Test]
+        public void MapWithOnlyKey_MessageValue()
+        {
+            // Hand-craft the stream to contain a single entry with just a key.
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+            output.WriteTag(TestMap.MapInt32ForeignMessageFieldNumber, WireFormat.WireType.LengthDelimited);
+            int key = 10;
+            output.WriteLength(1 + CodedOutputStream.ComputeInt32Size(key));
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(new ForeignMessage(), parsed.MapInt32ForeignMessage[key]);
+        }
+
+        [Test]
+        public void MapIgnoresExtraFieldsWithinEntryMessages()
+        {
+            // Hand-craft the stream to contain a single entry with three fields
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+
+            var key = 10; // Field 1 
+            var value = 20; // Field 2
+            var extra = 30; // Field 3
+
+            // Each field can be represented in a single byte, with a single byte tag.
+            // Total message size: 6 bytes.
+            output.WriteLength(6);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value);
+            output.WriteTag(3, WireFormat.WireType.Varint);
+            output.WriteInt32(extra);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(value, parsed.MapInt32Int32[key]);
+        }
+
+        [Test]
+        public void MapFieldOrderIsIrrelevant()
+        {
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+
+            var key = 10;
+            var value = 20;
+
+            // Each field can be represented in a single byte, with a single byte tag.
+            // Total message size: 4 bytes.
+            output.WriteLength(4);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(value, parsed.MapInt32Int32[key]);
+        }
+
+        [Test]
+        public void MapNonContiguousEntries()
+        {
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+
+            // Message structure:
+            // Entry for MapInt32Int32
+            // Entry for MapStringString
+            // Entry for MapInt32Int32
+
+            // First entry
+            var key1 = 10;
+            var value1 = 20;
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key1);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value1);
+
+            // Second entry
+            var key2 = "a";
+            var value2 = "b";
+            output.WriteTag(TestMap.MapStringStringFieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(6); // 3 bytes per entry: tag, size, character
+            output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteString(key2);
+            output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+            output.WriteString(value2);
+
+            // Third entry
+            var key3 = 15;
+            var value3 = 25;
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key3);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value3);
+
+            output.Flush();
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            var expected = new TestMap
+            {
+                MapInt32Int32 = { { key1, value1 }, { key3, value3 } },
+                MapStringString = { { key2, value2 } }
+            };
+            Assert.AreEqual(expected, parsed);
+        }
+
+        [Test]
+        public void DuplicateKeys_LastEntryWins()
+        {
+            var memoryStream = new MemoryStream();
+            var output = new CodedOutputStream(memoryStream);
+
+            var key = 10;
+            var value1 = 20;
+            var value2 = 30;
+
+            // First entry
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value1);
+
+            // Second entry - same key, different value
+            output.WriteTag(TestMap.MapInt32Int32FieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(4);
+            output.WriteTag(1, WireFormat.WireType.Varint);
+            output.WriteInt32(key);
+            output.WriteTag(2, WireFormat.WireType.Varint);
+            output.WriteInt32(value2);
+            output.Flush();
+
+            var parsed = TestMap.Parser.ParseFrom(memoryStream.ToArray());
+            Assert.AreEqual(value2, parsed.MapInt32Int32[key]);
+        }
+
+        [Test]
+        public void CloneSingleNonMessageValues()
+        {
+            var original = new TestAllTypes
+            {
+                SingleBool = true,
+                SingleBytes = ByteString.CopyFrom(1, 2, 3, 4),
+                SingleDouble = 23.5,
+                SingleFixed32 = 23,
+                SingleFixed64 = 1234567890123,
+                SingleFloat = 12.25f,
+                SingleInt32 = 100,
+                SingleInt64 = 3210987654321,
+                SingleNestedEnum = TestAllTypes.Types.NestedEnum.Foo,
+                SingleSfixed32 = -123,
+                SingleSfixed64 = -12345678901234,
+                SingleSint32 = -456,
+                SingleSint64 = -12345678901235,
+                SingleString = "test",
+                SingleUint32 = uint.MaxValue,
+                SingleUint64 = ulong.MaxValue
+            };
+            var clone = original.Clone();
+            Assert.AreNotSame(original, clone);
+            Assert.AreEqual(original, clone);
+            // Just as a single example
+            clone.SingleInt32 = 150;
+            Assert.AreNotEqual(original, clone);
+        }
+
+        [Test]
+        public void CloneRepeatedNonMessageValues()
+        {
+            var original = new TestAllTypes
+            {
+                RepeatedBool = { true, false },
+                RepeatedBytes = { ByteString.CopyFrom(1, 2, 3, 4), ByteString.CopyFrom(5, 6) },
+                RepeatedDouble = { -12.25, 23.5 },
+                RepeatedFixed32 = { uint.MaxValue, 23 },
+                RepeatedFixed64 = { ulong.MaxValue, 1234567890123 },
+                RepeatedFloat = { 100f, 12.25f },
+                RepeatedInt32 = { 100, 200 },
+                RepeatedInt64 = { 3210987654321, long.MaxValue },
+                RepeatedNestedEnum = { TestAllTypes.Types.NestedEnum.Foo, TestAllTypes.Types.NestedEnum.Neg },
+                RepeatedSfixed32 = { -123, 123 },
+                RepeatedSfixed64 = { -12345678901234, 12345678901234 },
+                RepeatedSint32 = { -456, 100 },
+                RepeatedSint64 = { -12345678901235, 123 },
+                RepeatedString = { "foo", "bar" },
+                RepeatedUint32 = { uint.MaxValue, uint.MinValue },
+                RepeatedUint64 = { ulong.MaxValue, uint.MinValue }
+            };
+
+            var clone = original.Clone();
+            Assert.AreNotSame(original, clone);
+            Assert.AreEqual(original, clone);
+            // Just as a single example
+            clone.RepeatedDouble.Add(25.5);
+            Assert.AreNotEqual(original, clone);
+        }
+
+        [Test]
+        public void CloneSingleMessageField()
+        {
+            var original = new TestAllTypes
+            {
+                SingleNestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 20 }
+            };
+
+            var clone = original.Clone();
+            Assert.AreNotSame(original, clone);
+            Assert.AreNotSame(original.SingleNestedMessage, clone.SingleNestedMessage);
+            Assert.AreEqual(original, clone);
+
+            clone.SingleNestedMessage.Bb = 30;
+            Assert.AreNotEqual(original, clone);
+        }
+
+        [Test]
+        public void CloneRepeatedMessageField()
+        {
+            var original = new TestAllTypes
+            {
+                RepeatedNestedMessage = { new TestAllTypes.Types.NestedMessage { Bb = 20 } }
+            };
+
+            var clone = original.Clone();
+            Assert.AreNotSame(original, clone);
+            Assert.AreNotSame(original.RepeatedNestedMessage, clone.RepeatedNestedMessage);
+            Assert.AreNotSame(original.RepeatedNestedMessage[0], clone.RepeatedNestedMessage[0]);
+            Assert.AreEqual(original, clone);
+
+            clone.RepeatedNestedMessage[0].Bb = 30;
+            Assert.AreNotEqual(original, clone);
+        }
+
+        [Test]
+        public void CloneOneofField()
+        {
+            var original = new TestAllTypes
+            {
+                OneofNestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 20 }
+            };
+
+            var clone = original.Clone();
+            Assert.AreNotSame(original, clone);
+            Assert.AreEqual(original, clone);
+
+            // We should have cloned the message
+            original.OneofNestedMessage.Bb = 30;
+            Assert.AreNotEqual(original, clone);
+        }
+
+        [Test]
+        public void OneofProperties()
+        {
+            // Switch the oneof case between each of the different options, and check everything behaves
+            // as expected in each case.
+            var message = new TestAllTypes();
+            Assert.AreEqual("", message.OneofString);
+            Assert.AreEqual(0, message.OneofUint32);
+            Assert.AreEqual(ByteString.Empty, message.OneofBytes);
+            Assert.IsNull(message.OneofNestedMessage);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.None, message.OneofFieldCase);
+
+            message.OneofString = "sample";
+            Assert.AreEqual("sample", message.OneofString);
+            Assert.AreEqual(0, message.OneofUint32);
+            Assert.AreEqual(ByteString.Empty, message.OneofBytes);
+            Assert.IsNull(message.OneofNestedMessage);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofString, message.OneofFieldCase);
+
+            var bytes = ByteString.CopyFrom(1, 2, 3);
+            message.OneofBytes = bytes;
+            Assert.AreEqual("", message.OneofString);
+            Assert.AreEqual(0, message.OneofUint32);
+            Assert.AreEqual(bytes, message.OneofBytes);
+            Assert.IsNull(message.OneofNestedMessage);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofBytes, message.OneofFieldCase);
+
+            message.OneofUint32 = 20;
+            Assert.AreEqual("", message.OneofString);
+            Assert.AreEqual(20, message.OneofUint32);
+            Assert.AreEqual(ByteString.Empty, message.OneofBytes);
+            Assert.IsNull(message.OneofNestedMessage);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofUint32, message.OneofFieldCase);
+
+            var nestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 25 };
+            message.OneofNestedMessage = nestedMessage;
+            Assert.AreEqual("", message.OneofString);
+            Assert.AreEqual(0, message.OneofUint32);
+            Assert.AreEqual(ByteString.Empty, message.OneofBytes);
+            Assert.AreEqual(nestedMessage, message.OneofNestedMessage);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofNestedMessage, message.OneofFieldCase);
+
+            message.ClearOneofField();
+            Assert.AreEqual("", message.OneofString);
+            Assert.AreEqual(0, message.OneofUint32);
+            Assert.AreEqual(ByteString.Empty, message.OneofBytes);
+            Assert.IsNull(message.OneofNestedMessage);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.None, message.OneofFieldCase);
+        }
+
+        [Test]
+        public void Oneof_DefaultValuesNotEqual()
+        {
+            var message1 = new TestAllTypes { OneofString = "" };
+            var message2 = new TestAllTypes { OneofUint32 = 0 };
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofString, message1.OneofFieldCase);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofUint32, message2.OneofFieldCase);
+            Assert.AreNotEqual(message1, message2);
+        }
+
+        [Test]
+        public void OneofSerialization_NonDefaultValue()
+        {
+            var message = new TestAllTypes();
+            message.OneofString = "this would take a bit of space";
+            message.OneofUint32 = 10;
+            var bytes = message.ToByteArray();
+            Assert.AreEqual(3, bytes.Length); // 2 bytes for the tag + 1 for the value - no string!
+
+            var message2 = TestAllTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, message2);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofUint32, message2.OneofFieldCase);
+        }
+
+        [Test]
+        public void OneofSerialization_DefaultValue()
+        {
+            var message = new TestAllTypes();
+            message.OneofString = "this would take a bit of space";
+            message.OneofUint32 = 0; // This is the default value for UInt32; normally wouldn't be serialized
+            var bytes = message.ToByteArray();
+            Assert.AreEqual(3, bytes.Length); // 2 bytes for the tag + 1 for the value - it's still serialized
+
+            var message2 = TestAllTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, message2);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.OneofUint32, message2.OneofFieldCase);
+        }
+
+        [Test]
+        public void DiscardUnknownFields_RealDataStillRead()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            var unusedFieldNumber = 23456;
+            Assert.IsFalse(TestAllTypes.Descriptor.Fields.InDeclarationOrder().Select(x => x.FieldNumber).Contains(unusedFieldNumber));
+            output.WriteTag(unusedFieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteString("ignore me");
+            message.WriteTo(output);
+            output.Flush();
+
+            stream.Position = 0;
+            var parsed = TestAllTypes.Parser.ParseFrom(stream);
+	    // TODO(jieluo): Add test back after DiscardUnknownFields is supported
+            // Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void DiscardUnknownFields_AllTypes()
+        {
+            // Simple way of ensuring we can skip all kinds of fields.
+            var data = SampleMessages.CreateFullTestAllTypes().ToByteArray();
+            var empty = Empty.Parser.ParseFrom(data);
+	    // TODO(jieluo): Add test back after DiscardUnknownField is supported.
+            // Assert.AreEqual(new Empty(), empty);
+        }
+
+        // This was originally seen as a conformance test failure.
+        [Test]
+        public void TruncatedMessageFieldThrows()
+        {
+            // 130, 3 is the message tag
+            // 1 is the data length - but there's no data.
+            var data = new byte[] { 130, 3, 1 };
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseFrom(data));
+        }
+
+        /// <summary>
+        /// Demonstrates current behaviour with an extraneous end group tag - see issue 688
+        /// for details; we may want to change this.
+        /// </summary>
+        [Test]
+        public void ExtraEndGroupThrows()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+
+            output.WriteTag(TestAllTypes.SingleFixed32FieldNumber, WireFormat.WireType.Fixed32);
+            output.WriteFixed32(123);
+            output.WriteTag(100, WireFormat.WireType.EndGroup);
+
+            output.Flush();
+
+            stream.Position = 0;
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseFrom(stream));
+        }
+
+        [Test]
+        public void CustomDiagnosticMessage_DirectToStringCall()
+        {
+            var message = new ForeignMessage { C = 31 };
+            Assert.AreEqual("{ \"c\": 31, \"@cInHex\": \"1f\" }", message.ToString());
+            Assert.AreEqual("{ \"c\": 31 }", JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        public void CustomDiagnosticMessage_Nested()
+        {
+            var message = new TestAllTypes { SingleForeignMessage = new ForeignMessage { C = 16 } };
+            Assert.AreEqual("{ \"singleForeignMessage\": { \"c\": 16, \"@cInHex\": \"10\" } }", message.ToString());
+            Assert.AreEqual("{ \"singleForeignMessage\": { \"c\": 16 } }", JsonFormatter.Default.Format(message));
+        }
+
+        [Test]
+        public void CustomDiagnosticMessage_DirectToTextWriterCall()
+        {
+            var message = new ForeignMessage { C = 31 };
+            var writer = new StringWriter();
+            JsonFormatter.Default.Format(message, writer);
+            Assert.AreEqual("{ \"c\": 31 }", writer.ToString());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj
new file mode 100644
index 0000000..06d07b9
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj
@@ -0,0 +1,30 @@
+﻿<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net451;netcoreapp1.0</TargetFrameworks>
+    <AssemblyOriginatorKeyFile>../../keys/Google.Protobuf.snk</AssemblyOriginatorKeyFile>
+    <SignAssembly>true</SignAssembly>
+    <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>
+    <IsPackable>False</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Google.Protobuf\Google.Protobuf.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="NUnit" Version="3.6.1" />
+    <PackageReference Include="NUnitLite" Version="3.6.1" />
+  </ItemGroup>
+
+  <!-- 
+    - Override target frameworks on non-Windows to just .NET Core
+    - Doing this conditionally in the initial PropertyGroup confuses
+    - Visual Studio.
+    -->
+  <PropertyGroup Condition="'$(OS)' != 'Windows_NT'">
+    <TargetFrameworks>netcoreapp1.0</TargetFrameworks>
+  </PropertyGroup>
+  
+</Project>
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/IssuesTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/IssuesTest.cs
new file mode 100644
index 0000000..a38d6b0
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/IssuesTest.cs
@@ -0,0 +1,82 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using Google.Protobuf.Reflection;
+using UnitTest.Issues.TestProtos;
+using NUnit.Framework;
+
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Tests for issues which aren't easily compartmentalized into other unit tests.
+    /// </summary>
+    public class IssuesTest
+    {
+        // Issue 45
+        [Test]
+        public void FieldCalledItem()
+        {
+            ItemField message = new ItemField { Item = 3 };
+            FieldDescriptor field = ItemField.Descriptor.FindFieldByName("item");
+            Assert.NotNull(field);
+            Assert.AreEqual(3, (int)field.Accessor.GetValue(message));
+        }
+
+        [Test]
+        public void ReservedNames()
+        {
+            var message = new ReservedNames { Types_ = 10, Descriptor_ = 20 };
+            // Underscores aren't reflected in the JSON.
+            Assert.AreEqual("{ \"types\": 10, \"descriptor\": 20 }", message.ToString());
+        }
+
+        [Test]
+        public void JsonNameParseTest()
+        {
+            var settings = new JsonParser.Settings(10, TypeRegistry.FromFiles(UnittestIssuesReflection.Descriptor));
+            var parser = new JsonParser(settings);
+
+            // It is safe to use either original field name or explicitly specified json_name
+            Assert.AreEqual(new TestJsonName { Name = "test", Description = "test2", Guid = "test3" },
+                parser.Parse<TestJsonName>("{ \"name\": \"test\", \"desc\": \"test2\", \"guid\": \"test3\" }"));
+        }
+
+        [Test]
+        public void JsonNameFormatTest()
+        {
+            var message = new TestJsonName { Name = "test", Description = "test2", Guid = "test3" };
+            Assert.AreEqual("{ \"name\": \"test\", \"desc\": \"test2\", \"exid\": \"test3\" }",
+                JsonFormatter.Default.Format(message));
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/JsonParserTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/JsonParserTest.cs
new file mode 100644
index 0000000..f595455
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/JsonParserTest.cs
@@ -0,0 +1,939 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using Google.Protobuf.Reflection;
+using Google.Protobuf.TestProtos;
+using Google.Protobuf.WellKnownTypes;
+using NUnit.Framework;
+using System;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Unit tests for JSON parsing.
+    /// </summary>
+    public class JsonParserTest
+    {
+        // Sanity smoke test
+        [Test]
+        public void AllTypesRoundtrip()
+        {
+            AssertRoundtrip(SampleMessages.CreateFullTestAllTypes());
+        }
+
+        [Test]
+        public void Maps()
+        {
+            AssertRoundtrip(new TestMap { MapStringString = { { "with spaces", "bar" }, { "a", "b" } } });
+            AssertRoundtrip(new TestMap { MapInt32Int32 = { { 0, 1 }, { 2, 3 } } });
+            AssertRoundtrip(new TestMap { MapBoolBool = { { false, true }, { true, false } } });
+        }
+
+        [Test]
+        [TestCase(" 1 ")]
+        [TestCase("+1")]
+        [TestCase("1,000")]
+        [TestCase("1.5")]
+        public void IntegerMapKeysAreStrict(string keyText)
+        {
+            // Test that integer parsing is strict. We assume that if this is correct for int32,
+            // it's correct for other numeric key types.
+            var json = "{ \"mapInt32Int32\": { \"" + keyText + "\" : \"1\" } }";
+            Assert.Throws<InvalidProtocolBufferException>(() => JsonParser.Default.Parse<TestMap>(json));
+        }
+
+        [Test]
+        public void OriginalFieldNameAccepted()
+        {
+            var json = "{ \"single_int32\": 10 }";
+            var expected = new TestAllTypes { SingleInt32 = 10 };
+            Assert.AreEqual(expected, TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void SourceContextRoundtrip()
+        {
+            AssertRoundtrip(new SourceContext { FileName = "foo.proto" });
+        }
+
+        [Test]
+        public void SingularWrappers_DefaultNonNullValues()
+        {
+            var message = new TestWellKnownTypes
+            {
+                StringField = "",
+                BytesField = ByteString.Empty,
+                BoolField = false,
+                FloatField = 0f,
+                DoubleField = 0d,
+                Int32Field = 0,
+                Int64Field = 0,
+                Uint32Field = 0,
+                Uint64Field = 0
+            };
+            AssertRoundtrip(message);
+        }
+
+        [Test]
+        public void SingularWrappers_NonDefaultValues()
+        {
+            var message = new TestWellKnownTypes
+            {
+                StringField = "x",
+                BytesField = ByteString.CopyFrom(1, 2, 3),
+                BoolField = true,
+                FloatField = 12.5f,
+                DoubleField = 12.25d,
+                Int32Field = 1,
+                Int64Field = 2,
+                Uint32Field = 3,
+                Uint64Field = 4
+            };
+            AssertRoundtrip(message);
+        }
+
+        [Test]
+        public void SingularWrappers_ExplicitNulls()
+        {
+            // When we parse the "valueField": null part, we remember it... basically, it's one case
+            // where explicit default values don't fully roundtrip.
+            var message = new TestWellKnownTypes { ValueField = Value.ForNull() };
+            var json = new JsonFormatter(new JsonFormatter.Settings(true)).Format(message);
+            var parsed = JsonParser.Default.Parse<TestWellKnownTypes>(json);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        [TestCase(typeof(BoolValue), "true", true)]
+        [TestCase(typeof(Int32Value), "32", 32)]
+        [TestCase(typeof(Int64Value), "32", 32L)]
+        [TestCase(typeof(Int64Value), "\"32\"", 32L)]
+        [TestCase(typeof(UInt32Value), "32", 32U)]
+        [TestCase(typeof(UInt64Value), "\"32\"", 32UL)]
+        [TestCase(typeof(UInt64Value), "32", 32UL)]
+        [TestCase(typeof(StringValue), "\"foo\"", "foo")]
+        [TestCase(typeof(FloatValue), "1.5", 1.5f)]
+        [TestCase(typeof(DoubleValue), "1.5", 1.5d)]
+        public void Wrappers_Standalone(System.Type wrapperType, string json, object expectedValue)
+        {
+            IMessage parsed = (IMessage)Activator.CreateInstance(wrapperType);
+            IMessage expected = (IMessage)Activator.CreateInstance(wrapperType);
+            JsonParser.Default.Merge(parsed, "null");
+            Assert.AreEqual(expected, parsed);
+
+            JsonParser.Default.Merge(parsed, json);
+            expected.Descriptor.Fields[WrappersReflection.WrapperValueFieldNumber].Accessor.SetValue(expected, expectedValue);
+            Assert.AreEqual(expected, parsed);
+        }
+
+        [Test]
+        public void ExplicitNullValue()
+        {
+            string json = "{\"valueField\": null}";
+            var message = JsonParser.Default.Parse<TestWellKnownTypes>(json);
+            Assert.AreEqual(new TestWellKnownTypes { ValueField = Value.ForNull() }, message);
+        }
+
+        [Test]
+        public void BytesWrapper_Standalone()
+        {
+            ByteString data = ByteString.CopyFrom(1, 2, 3);
+            // Can't do this with attributes...
+            var parsed = JsonParser.Default.Parse<BytesValue>(WrapInQuotes(data.ToBase64()));
+            var expected = new BytesValue { Value = data };
+            Assert.AreEqual(expected, parsed);
+        }
+
+        [Test]
+        public void RepeatedWrappers()
+        {
+            var message = new RepeatedWellKnownTypes
+            {
+                BoolField = { true, false },
+                BytesField = { ByteString.CopyFrom(1, 2, 3), ByteString.CopyFrom(4, 5, 6), ByteString.Empty },
+                DoubleField = { 12.5, -1.5, 0d },
+                FloatField = { 123.25f, -20f, 0f },
+                Int32Field = { int.MaxValue, int.MinValue, 0 },
+                Int64Field = { long.MaxValue, long.MinValue, 0L },
+                StringField = { "First", "Second", "" },
+                Uint32Field = { uint.MaxValue, uint.MinValue, 0U },
+                Uint64Field = { ulong.MaxValue, ulong.MinValue, 0UL },
+            };
+            AssertRoundtrip(message);
+        }
+
+        [Test]
+        public void RepeatedField_NullElementProhibited()
+        {
+            string json = "{ \"repeated_foreign_message\": [null] }";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void RepeatedField_NullOverallValueAllowed()
+        {
+            string json = "{ \"repeated_foreign_message\": null }";
+            Assert.AreEqual(new TestAllTypes(), TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("{ \"mapInt32Int32\": { \"10\": null }")]
+        [TestCase("{ \"mapStringString\": { \"abc\": null }")]
+        [TestCase("{ \"mapInt32ForeignMessage\": { \"10\": null }")]
+        public void MapField_NullValueProhibited(string json)
+        {
+            Assert.Throws<InvalidProtocolBufferException>(() => TestMap.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void MapField_NullOverallValueAllowed()
+        {
+            string json = "{ \"mapInt32Int32\": null }";
+            Assert.AreEqual(new TestMap(), TestMap.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void IndividualWrapperTypes()
+        {
+            Assert.AreEqual(new StringValue { Value = "foo" }, StringValue.Parser.ParseJson("\"foo\""));
+            Assert.AreEqual(new Int32Value { Value = 1 }, Int32Value.Parser.ParseJson("1"));
+            // Can parse strings directly too
+            Assert.AreEqual(new Int32Value { Value = 1 }, Int32Value.Parser.ParseJson("\"1\""));
+        }
+
+        private static void AssertRoundtrip<T>(T message) where T : IMessage<T>, new()
+        {
+            var clone = message.Clone();
+            var json = JsonFormatter.Default.Format(message);
+            var parsed = JsonParser.Default.Parse<T>(json);
+            Assert.AreEqual(clone, parsed);
+        }
+
+        [Test]
+        [TestCase("0", 0)]
+        [TestCase("-0", 0)] // Not entirely clear whether we intend to allow this...
+        [TestCase("1", 1)]
+        [TestCase("-1", -1)]
+        [TestCase("2147483647", 2147483647)]
+        [TestCase("-2147483648", -2147483648)]
+        public void StringToInt32_Valid(string jsonValue, int expectedParsedValue)
+        {
+            string json = "{ \"singleInt32\": \"" + jsonValue + "\"}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleInt32);
+        }
+
+        [Test]
+        [TestCase("+0")]
+        [TestCase(" 1")]
+        [TestCase("1 ")]
+        [TestCase("00")]
+        [TestCase("-00")]
+        [TestCase("--1")]
+        [TestCase("+1")]
+        [TestCase("1.5")]
+        [TestCase("1e10")]
+        [TestCase("2147483648")]
+        [TestCase("-2147483649")]
+        public void StringToInt32_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleInt32\": \"" + jsonValue + "\"}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0U)]
+        [TestCase("1", 1U)]
+        [TestCase("4294967295", 4294967295U)]
+        public void StringToUInt32_Valid(string jsonValue, uint expectedParsedValue)
+        {
+            string json = "{ \"singleUint32\": \"" + jsonValue + "\"}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleUint32);
+        }
+
+        // Assume that anything non-bounds-related is covered in the Int32 case
+        [Test]
+        [TestCase("-1")]
+        [TestCase("4294967296")]
+        public void StringToUInt32_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleUint32\": \"" + jsonValue + "\"}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0L)]
+        [TestCase("1", 1L)]
+        [TestCase("-1", -1L)]
+        [TestCase("9223372036854775807", 9223372036854775807)]
+        [TestCase("-9223372036854775808", -9223372036854775808)]
+        public void StringToInt64_Valid(string jsonValue, long expectedParsedValue)
+        {
+            string json = "{ \"singleInt64\": \"" + jsonValue + "\"}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleInt64);
+        }
+
+        // Assume that anything non-bounds-related is covered in the Int32 case
+        [Test]
+        [TestCase("-9223372036854775809")]
+        [TestCase("9223372036854775808")]
+        public void StringToInt64_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleInt64\": \"" + jsonValue + "\"}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0UL)]
+        [TestCase("1", 1UL)]
+        [TestCase("18446744073709551615", 18446744073709551615)]
+        public void StringToUInt64_Valid(string jsonValue, ulong expectedParsedValue)
+        {
+            string json = "{ \"singleUint64\": \"" + jsonValue + "\"}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleUint64);
+        }
+
+        // Assume that anything non-bounds-related is covered in the Int32 case
+        [Test]
+        [TestCase("-1")]
+        [TestCase("18446744073709551616")]
+        public void StringToUInt64_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleUint64\": \"" + jsonValue + "\"}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0d)]
+        [TestCase("1", 1d)]
+        [TestCase("1.000000", 1d)]
+        [TestCase("1.0000000000000000000000001", 1d)] // We don't notice that we haven't preserved the exact value
+        [TestCase("-1", -1d)]
+        [TestCase("1e1", 10d)]
+        [TestCase("1e01", 10d)] // Leading decimals are allowed in exponents
+        [TestCase("1E1", 10d)] // Either case is fine
+        [TestCase("-1e1", -10d)]
+        [TestCase("1.5e1", 15d)]
+        [TestCase("-1.5e1", -15d)]
+        [TestCase("15e-1", 1.5d)]
+        [TestCase("-15e-1", -1.5d)]
+        [TestCase("1.79769e308", 1.79769e308)]
+        [TestCase("-1.79769e308", -1.79769e308)]
+        [TestCase("Infinity", double.PositiveInfinity)]
+        [TestCase("-Infinity", double.NegativeInfinity)]
+        [TestCase("NaN", double.NaN)]
+        public void StringToDouble_Valid(string jsonValue, double expectedParsedValue)
+        {
+            string json = "{ \"singleDouble\": \"" + jsonValue + "\"}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleDouble);
+        }
+
+        [Test]
+        [TestCase("1.7977e308")]
+        [TestCase("-1.7977e308")]
+        [TestCase("1e309")]
+        [TestCase("1,0")]
+        [TestCase("1.0.0")]
+        [TestCase("+1")]
+        [TestCase("00")]
+        [TestCase("01")]
+        [TestCase("-00")]
+        [TestCase("-01")]
+        [TestCase("--1")]
+        [TestCase(" Infinity")]
+        [TestCase(" -Infinity")]
+        [TestCase("NaN ")]
+        [TestCase("Infinity ")]
+        [TestCase("-Infinity ")]
+        [TestCase(" NaN")]
+        [TestCase("INFINITY")]
+        [TestCase("nan")]
+        [TestCase("\u00BD")] // 1/2 as a single Unicode character. Just sanity checking...
+        public void StringToDouble_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleDouble\": \"" + jsonValue + "\"}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0f)]
+        [TestCase("1", 1f)]
+        [TestCase("1.000000", 1f)]
+        [TestCase("-1", -1f)]
+        [TestCase("3.402823e38", 3.402823e38f)]
+        [TestCase("-3.402823e38", -3.402823e38f)]
+        [TestCase("1.5e1", 15f)]
+        [TestCase("15e-1", 1.5f)]
+        public void StringToFloat_Valid(string jsonValue, float expectedParsedValue)
+        {
+            string json = "{ \"singleFloat\": \"" + jsonValue + "\"}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleFloat);
+        }
+
+        [Test]
+        [TestCase("3.402824e38")]
+        [TestCase("-3.402824e38")]
+        [TestCase("1,0")]
+        [TestCase("1.0.0")]
+        [TestCase("+1")]
+        [TestCase("00")]
+        [TestCase("--1")]
+        public void StringToFloat_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleFloat\": \"" + jsonValue + "\"}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0)]
+        [TestCase("-0", 0)] // Not entirely clear whether we intend to allow this...
+        [TestCase("1", 1)]
+        [TestCase("-1", -1)]
+        [TestCase("2147483647", 2147483647)]
+        [TestCase("-2147483648", -2147483648)]
+        [TestCase("1e1", 10)]
+        [TestCase("-1e1", -10)]
+        [TestCase("10.00", 10)]
+        [TestCase("-10.00", -10)]
+        public void NumberToInt32_Valid(string jsonValue, int expectedParsedValue)
+        {
+            string json = "{ \"singleInt32\": " + jsonValue + "}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleInt32);
+        }
+
+        [Test]
+        [TestCase("+0", typeof(InvalidJsonException))]
+        [TestCase("00", typeof(InvalidJsonException))]
+        [TestCase("-00", typeof(InvalidJsonException))]
+        [TestCase("--1", typeof(InvalidJsonException))]
+        [TestCase("+1", typeof(InvalidJsonException))]
+        [TestCase("1.5", typeof(InvalidProtocolBufferException))]
+        // Value is out of range
+        [TestCase("1e10", typeof(InvalidProtocolBufferException))]
+        [TestCase("2147483648", typeof(InvalidProtocolBufferException))]
+        [TestCase("-2147483649", typeof(InvalidProtocolBufferException))]
+        public void NumberToInt32_Invalid(string jsonValue, System.Type expectedExceptionType)
+        {
+            string json = "{ \"singleInt32\": " + jsonValue + "}";
+            Assert.Throws(expectedExceptionType, () => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0U)]
+        [TestCase("1", 1U)]
+        [TestCase("4294967295", 4294967295U)]
+        public void NumberToUInt32_Valid(string jsonValue, uint expectedParsedValue)
+        {
+            string json = "{ \"singleUint32\": " + jsonValue + "}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleUint32);
+        }
+
+        // Assume that anything non-bounds-related is covered in the Int32 case
+        [Test]
+        [TestCase("-1")]
+        [TestCase("4294967296")]
+        public void NumberToUInt32_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleUint32\": " + jsonValue + "}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0L)]
+        [TestCase("1", 1L)]
+        [TestCase("-1", -1L)]
+        // long.MaxValue isn't actually representable as a double. This string value is the highest
+        // representable value which isn't greater than long.MaxValue.
+        [TestCase("9223372036854774784", 9223372036854774784)]
+        [TestCase("-9223372036854775808", -9223372036854775808)]
+        public void NumberToInt64_Valid(string jsonValue, long expectedParsedValue)
+        {
+            string json = "{ \"singleInt64\": " + jsonValue + "}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleInt64);
+        }
+
+        // Assume that anything non-bounds-related is covered in the Int32 case
+        [Test]
+        [TestCase("9223372036854775808")]
+        // Theoretical bound would be -9223372036854775809, but when that is parsed to a double
+        // we end up with the exact value of long.MinValue due to lack of precision. The value here
+        // is the "next double down".
+        [TestCase("-9223372036854780000")]
+        public void NumberToInt64_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleInt64\": " + jsonValue + "}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0UL)]
+        [TestCase("1", 1UL)]
+        // ulong.MaxValue isn't representable as a double. This value is the largest double within
+        // the range of ulong.
+        [TestCase("18446744073709549568", 18446744073709549568UL)]
+        public void NumberToUInt64_Valid(string jsonValue, ulong expectedParsedValue)
+        {
+            string json = "{ \"singleUint64\": " + jsonValue + "}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleUint64);
+        }
+
+        // Assume that anything non-bounds-related is covered in the Int32 case
+        [Test]
+        [TestCase("-1")]
+        [TestCase("18446744073709551616")]
+        public void NumberToUInt64_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleUint64\": " + jsonValue + "}";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0d)]
+        [TestCase("1", 1d)]
+        [TestCase("1.000000", 1d)]
+        [TestCase("1.0000000000000000000000001", 1d)] // We don't notice that we haven't preserved the exact value
+        [TestCase("-1", -1d)]
+        [TestCase("1e1", 10d)]
+        [TestCase("1e01", 10d)] // Leading decimals are allowed in exponents
+        [TestCase("1E1", 10d)] // Either case is fine
+        [TestCase("-1e1", -10d)]
+        [TestCase("1.5e1", 15d)]
+        [TestCase("-1.5e1", -15d)]
+        [TestCase("15e-1", 1.5d)]
+        [TestCase("-15e-1", -1.5d)]
+        [TestCase("1.79769e308", 1.79769e308)]
+        [TestCase("-1.79769e308", -1.79769e308)]
+        public void NumberToDouble_Valid(string jsonValue, double expectedParsedValue)
+        {
+            string json = "{ \"singleDouble\": " + jsonValue + "}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleDouble);
+        }
+
+        [Test]
+        [TestCase("1.7977e308")]
+        [TestCase("-1.7977e308")]
+        [TestCase("1e309")]
+        [TestCase("1,0")]
+        [TestCase("1.0.0")]
+        [TestCase("+1")]
+        [TestCase("00")]
+        [TestCase("--1")]
+        [TestCase("\u00BD")] // 1/2 as a single Unicode character. Just sanity checking...
+        public void NumberToDouble_Invalid(string jsonValue)
+        {
+            string json = "{ \"singleDouble\": " + jsonValue + "}";
+            Assert.Throws<InvalidJsonException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("0", 0f)]
+        [TestCase("1", 1f)]
+        [TestCase("1.000000", 1f)]
+        [TestCase("-1", -1f)]
+        [TestCase("3.402823e38", 3.402823e38f)]
+        [TestCase("-3.402823e38", -3.402823e38f)]
+        [TestCase("1.5e1", 15f)]
+        [TestCase("15e-1", 1.5f)]
+        public void NumberToFloat_Valid(string jsonValue, float expectedParsedValue)
+        {
+            string json = "{ \"singleFloat\": " + jsonValue + "}";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(expectedParsedValue, parsed.SingleFloat);
+        }
+
+        [Test]
+        [TestCase("3.402824e38", typeof(InvalidProtocolBufferException))]
+        [TestCase("-3.402824e38", typeof(InvalidProtocolBufferException))]
+        [TestCase("1,0", typeof(InvalidJsonException))]
+        [TestCase("1.0.0", typeof(InvalidJsonException))]
+        [TestCase("+1", typeof(InvalidJsonException))]
+        [TestCase("00", typeof(InvalidJsonException))]
+        [TestCase("--1", typeof(InvalidJsonException))]
+        public void NumberToFloat_Invalid(string jsonValue, System.Type expectedExceptionType)
+        {
+            string json = "{ \"singleFloat\": " + jsonValue + "}";
+            Assert.Throws(expectedExceptionType, () => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        // The simplest way of testing that the value has parsed correctly is to reformat it,
+        // as we trust the formatting. In many cases that will give the same result as the input,
+        // so in those cases we accept an expectedFormatted value of null. Sometimes the results
+        // will be different though, due to a different number of digits being provided.
+        [Test]
+        // Z offset
+        [TestCase("2015-10-09T14:46:23.123456789Z", null)]
+        [TestCase("2015-10-09T14:46:23.123456Z", null)]
+        [TestCase("2015-10-09T14:46:23.123Z", null)]
+        [TestCase("2015-10-09T14:46:23Z", null)]
+        [TestCase("2015-10-09T14:46:23.123456000Z", "2015-10-09T14:46:23.123456Z")]
+        [TestCase("2015-10-09T14:46:23.1234560Z", "2015-10-09T14:46:23.123456Z")]
+        [TestCase("2015-10-09T14:46:23.123000000Z", "2015-10-09T14:46:23.123Z")]
+        [TestCase("2015-10-09T14:46:23.1230Z", "2015-10-09T14:46:23.123Z")]
+        [TestCase("2015-10-09T14:46:23.00Z", "2015-10-09T14:46:23Z")]
+
+        // +00:00 offset
+        [TestCase("2015-10-09T14:46:23.123456789+00:00", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-09T14:46:23.123456+00:00", "2015-10-09T14:46:23.123456Z")]
+        [TestCase("2015-10-09T14:46:23.123+00:00", "2015-10-09T14:46:23.123Z")]
+        [TestCase("2015-10-09T14:46:23+00:00", "2015-10-09T14:46:23Z")]
+        [TestCase("2015-10-09T14:46:23.123456000+00:00", "2015-10-09T14:46:23.123456Z")]
+        [TestCase("2015-10-09T14:46:23.1234560+00:00", "2015-10-09T14:46:23.123456Z")]
+        [TestCase("2015-10-09T14:46:23.123000000+00:00", "2015-10-09T14:46:23.123Z")]
+        [TestCase("2015-10-09T14:46:23.1230+00:00", "2015-10-09T14:46:23.123Z")]
+        [TestCase("2015-10-09T14:46:23.00+00:00", "2015-10-09T14:46:23Z")]
+
+        // Other offsets (assume by now that the subsecond handling is okay)
+        [TestCase("2015-10-09T15:46:23.123456789+01:00", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-09T13:46:23.123456789-01:00", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-09T15:16:23.123456789+00:30", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-09T14:16:23.123456789-00:30", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-09T16:31:23.123456789+01:45", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-09T13:01:23.123456789-01:45", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-10T08:46:23.123456789+18:00", "2015-10-09T14:46:23.123456789Z")]
+        [TestCase("2015-10-08T20:46:23.123456789-18:00", "2015-10-09T14:46:23.123456789Z")]
+
+        // Leap years and min/max
+        [TestCase("2016-02-29T14:46:23.123456789Z", null)]
+        [TestCase("2000-02-29T14:46:23.123456789Z", null)]
+        [TestCase("0001-01-01T00:00:00Z", null)]
+        [TestCase("9999-12-31T23:59:59.999999999Z", null)]
+        public void Timestamp_Valid(string jsonValue, string expectedFormatted)
+        {
+            expectedFormatted = expectedFormatted ?? jsonValue;
+            string json = WrapInQuotes(jsonValue);
+            var parsed = Timestamp.Parser.ParseJson(json);
+            Assert.AreEqual(WrapInQuotes(expectedFormatted), parsed.ToString());
+        }
+
+        [Test]
+        [TestCase("2015-10-09 14:46:23.123456789Z", Description = "No T between date and time")]
+        [TestCase("2015/10/09T14:46:23.123456789Z", Description = "Wrong date separators")]
+        [TestCase("2015-10-09T14.46.23.123456789Z", Description = "Wrong time separators")]
+        [TestCase("2015-10-09T14:46:23,123456789Z", Description = "Wrong fractional second separators (valid ISO-8601 though)")]
+        [TestCase(" 2015-10-09T14:46:23.123456789Z", Description = "Whitespace at start")]
+        [TestCase("2015-10-09T14:46:23.123456789Z ", Description = "Whitespace at end")]
+        [TestCase("2015-10-09T14:46:23.1234567890", Description = "Too many digits")]
+        [TestCase("2015-10-09T14:46:23.123456789", Description = "No offset")]
+        [TestCase("2015-13-09T14:46:23.123456789Z", Description = "Invalid month")]
+        [TestCase("2015-10-32T14:46:23.123456789Z", Description = "Invalid day")]
+        [TestCase("2015-10-09T24:00:00.000000000Z", Description = "Invalid hour (valid ISO-8601 though)")]
+        [TestCase("2015-10-09T14:60:23.123456789Z", Description = "Invalid minutes")]
+        [TestCase("2015-10-09T14:46:60.123456789Z", Description = "Invalid seconds")]
+        [TestCase("2015-10-09T14:46:23.123456789+18:01", Description = "Offset too large (positive)")]
+        [TestCase("2015-10-09T14:46:23.123456789-18:01", Description = "Offset too large (negative)")]
+        [TestCase("2015-10-09T14:46:23.123456789-00:00", Description = "Local offset (-00:00) makes no sense here")]
+        [TestCase("0001-01-01T00:00:00+00:01", Description = "Value before earliest when offset applied")]
+        [TestCase("9999-12-31T23:59:59.999999999-00:01", Description = "Value after latest when offset applied")]
+        [TestCase("2100-02-29T14:46:23.123456789Z", Description = "Feb 29th on a non-leap-year")]
+        public void Timestamp_Invalid(string jsonValue)
+        {
+            string json = WrapInQuotes(jsonValue);
+            Assert.Throws<InvalidProtocolBufferException>(() => Timestamp.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void StructValue_Null()
+        {
+            Assert.AreEqual(new Value { NullValue = 0 }, Value.Parser.ParseJson("null"));
+        }
+
+        [Test]
+        public void StructValue_String()
+        {
+            Assert.AreEqual(new Value { StringValue = "hi" }, Value.Parser.ParseJson("\"hi\""));
+        }
+
+        [Test]
+        public void StructValue_Bool()
+        {
+            Assert.AreEqual(new Value { BoolValue = true }, Value.Parser.ParseJson("true"));
+            Assert.AreEqual(new Value { BoolValue = false }, Value.Parser.ParseJson("false"));
+        }
+
+        [Test]
+        public void StructValue_List()
+        {
+            Assert.AreEqual(Value.ForList(Value.ForNumber(1), Value.ForString("x")), Value.Parser.ParseJson("[1, \"x\"]"));
+        }
+
+        [Test]
+        public void ParseListValue()
+        {
+            Assert.AreEqual(new ListValue { Values = { Value.ForNumber(1), Value.ForString("x") } }, ListValue.Parser.ParseJson("[1, \"x\"]"));
+        }
+
+        [Test]
+        public void StructValue_Struct()
+        {
+            Assert.AreEqual(
+                Value.ForStruct(new Struct { Fields = { { "x", Value.ForNumber(1) }, { "y", Value.ForString("z") } } }),
+                Value.Parser.ParseJson("{ \"x\": 1, \"y\": \"z\" }"));
+        }
+
+        [Test]
+        public void ParseStruct()
+        {
+            Assert.AreEqual(new Struct { Fields = { { "x", Value.ForNumber(1) }, { "y", Value.ForString("z") } } },
+                Struct.Parser.ParseJson("{ \"x\": 1, \"y\": \"z\" }"));
+        }
+
+        // TODO for duration parsing: upper and lower bounds.
+        // +/- 315576000000 seconds
+
+        [Test]
+        [TestCase("1.123456789s", null)]
+        [TestCase("1.123456s", null)]
+        [TestCase("1.123s", null)]
+        [TestCase("1.12300s", "1.123s")]
+        [TestCase("1.12345s", "1.123450s")]
+        [TestCase("1s", null)]
+        [TestCase("-1.123456789s", null)]
+        [TestCase("-1.123456s", null)]
+        [TestCase("-1.123s", null)]
+        [TestCase("-1s", null)]
+        [TestCase("0.123s", null)]
+        [TestCase("-0.123s", null)]
+        [TestCase("123456.123s", null)]
+        [TestCase("-123456.123s", null)]
+        // Upper and lower bounds
+        [TestCase("315576000000s", null)]
+        [TestCase("-315576000000s", null)]
+        public void Duration_Valid(string jsonValue, string expectedFormatted)
+        {
+            expectedFormatted = expectedFormatted ?? jsonValue;
+            string json = WrapInQuotes(jsonValue);
+            var parsed = Duration.Parser.ParseJson(json);
+            Assert.AreEqual(WrapInQuotes(expectedFormatted), parsed.ToString());
+        }
+
+        // The simplest way of testing that the value has parsed correctly is to reformat it,
+        // as we trust the formatting. In many cases that will give the same result as the input,
+        // so in those cases we accept an expectedFormatted value of null. Sometimes the results
+        // will be different though, due to a different number of digits being provided.
+        [Test]
+        [TestCase("1.1234567890s", Description = "Too many digits")]
+        [TestCase("1.123456789", Description = "No suffix")]
+        [TestCase("1.123456789ss", Description = "Too much suffix")]
+        [TestCase("1.123456789S", Description = "Upper case suffix")]
+        [TestCase("+1.123456789s", Description = "Leading +")]
+        [TestCase(".123456789s", Description = "No integer before the fraction")]
+        [TestCase("1,123456789s", Description = "Comma as decimal separator")]
+        [TestCase("1x1.123456789s", Description = "Non-digit in integer part")]
+        [TestCase("1.1x3456789s", Description = "Non-digit in fractional part")]
+        [TestCase(" 1.123456789s", Description = "Whitespace before fraction")]
+        [TestCase("1.123456789s ", Description = "Whitespace after value")]
+        [TestCase("01.123456789s", Description = "Leading zero (positive)")]
+        [TestCase("-01.123456789s", Description = "Leading zero (negative)")]
+        [TestCase("--0.123456789s", Description = "Double minus sign")]
+        // Violate upper/lower bounds in various ways
+        [TestCase("315576000001s", Description = "Integer part too large")]
+        [TestCase("3155760000000s", Description = "Integer part too long (positive)")]
+        [TestCase("-3155760000000s", Description = "Integer part too long (negative)")]
+        public void Duration_Invalid(string jsonValue)
+        {
+            string json = WrapInQuotes(jsonValue);
+            Assert.Throws<InvalidProtocolBufferException>(() => Duration.Parser.ParseJson(json));
+        }
+
+        // Not as many tests for field masks as I'd like; more to be added when we have more
+        // detailed specifications.
+
+        [Test]
+        [TestCase("")]
+        [TestCase("foo", "foo")]
+        [TestCase("foo,bar", "foo", "bar")]
+        [TestCase("foo.bar", "foo.bar")]
+        [TestCase("fooBar", "foo_bar")]
+        [TestCase("fooBar.bazQux", "foo_bar.baz_qux")]
+        public void FieldMask_Valid(string jsonValue, params string[] expectedPaths)
+        {
+            string json = WrapInQuotes(jsonValue);
+            var parsed = FieldMask.Parser.ParseJson(json);
+            CollectionAssert.AreEqual(expectedPaths, parsed.Paths);
+        }
+
+        [Test]
+        [TestCase("foo_bar")]
+        public void FieldMask_Invalid(string jsonValue)
+        {
+            string json = WrapInQuotes(jsonValue);
+            Assert.Throws<InvalidProtocolBufferException>(() => FieldMask.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void Any_RegularMessage()
+        {
+            var registry = TypeRegistry.FromMessages(TestAllTypes.Descriptor);
+            var formatter = new JsonFormatter(new JsonFormatter.Settings(false, TypeRegistry.FromMessages(TestAllTypes.Descriptor)));
+            var message = new TestAllTypes { SingleInt32 = 10, SingleNestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 20 } };
+            var original = Any.Pack(message);
+            var json = formatter.Format(original); // This is tested in JsonFormatterTest
+            var parser = new JsonParser(new JsonParser.Settings(10, registry));
+            Assert.AreEqual(original, parser.Parse<Any>(json));
+            string valueFirstJson = "{ \"singleInt32\": 10, \"singleNestedMessage\": { \"bb\": 20 }, \"@type\": \"type.googleapis.com/protobuf_unittest.TestAllTypes\" }";
+            Assert.AreEqual(original, parser.Parse<Any>(valueFirstJson));
+        }
+
+        [Test]
+        public void Any_CustomPrefix()
+        {
+            var registry = TypeRegistry.FromMessages(TestAllTypes.Descriptor);
+            var message = new TestAllTypes { SingleInt32 = 10 };
+            var original = Any.Pack(message, "custom.prefix/middle-part");
+            var parser = new JsonParser(new JsonParser.Settings(10, registry));
+            string json = "{ \"@type\": \"custom.prefix/middle-part/protobuf_unittest.TestAllTypes\", \"singleInt32\": 10 }";
+            Assert.AreEqual(original, parser.Parse<Any>(json));
+        }
+
+        [Test]
+        public void Any_UnknownType()
+        {
+            string json = "{ \"@type\": \"type.googleapis.com/bogus\" }";
+            Assert.Throws<InvalidOperationException>(() => Any.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void Any_NoTypeUrl()
+        {
+            string json = "{ \"foo\": \"bar\" }";
+            Assert.Throws<InvalidProtocolBufferException>(() => Any.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void Any_WellKnownType()
+        {
+            var registry = TypeRegistry.FromMessages(Timestamp.Descriptor);
+            var formatter = new JsonFormatter(new JsonFormatter.Settings(false, registry));
+            var timestamp = new DateTime(1673, 6, 19, 12, 34, 56, DateTimeKind.Utc).ToTimestamp();
+            var original = Any.Pack(timestamp);
+            var json = formatter.Format(original); // This is tested in JsonFormatterTest
+            var parser = new JsonParser(new JsonParser.Settings(10, registry));
+            Assert.AreEqual(original, parser.Parse<Any>(json));
+            string valueFirstJson = "{ \"value\": \"1673-06-19T12:34:56Z\", \"@type\": \"type.googleapis.com/google.protobuf.Timestamp\" }";
+            Assert.AreEqual(original, parser.Parse<Any>(valueFirstJson));
+        }
+
+        [Test]
+        public void Any_Nested()
+        {
+            var registry = TypeRegistry.FromMessages(TestWellKnownTypes.Descriptor, TestAllTypes.Descriptor);
+            var formatter = new JsonFormatter(new JsonFormatter.Settings(false, registry));
+            var parser = new JsonParser(new JsonParser.Settings(10, registry));
+            var doubleNestedMessage = new TestAllTypes { SingleInt32 = 20 };
+            var nestedMessage = Any.Pack(doubleNestedMessage);
+            var message = new TestWellKnownTypes { AnyField = Any.Pack(nestedMessage) };
+            var json = formatter.Format(message);
+            // Use the descriptor-based parser just for a change.
+            Assert.AreEqual(message, parser.Parse(json, TestWellKnownTypes.Descriptor));
+        }
+
+        [Test]
+        public void DataAfterObject()
+        {
+            string json = "{} 10";
+            Assert.Throws<InvalidJsonException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        /// <summary>
+        /// JSON equivalent to <see cref="CodedInputStreamTest.MaliciousRecursion"/>
+        /// </summary>
+        [Test]
+        public void MaliciousRecursion()
+        {
+            string data64 = CodedInputStreamTest.MakeRecursiveMessage(64).ToString();
+            string data65 = CodedInputStreamTest.MakeRecursiveMessage(65).ToString();
+
+            var parser64 = new JsonParser(new JsonParser.Settings(64));
+            CodedInputStreamTest.AssertMessageDepth(parser64.Parse<TestRecursiveMessage>(data64), 64);
+            Assert.Throws<InvalidProtocolBufferException>(() => parser64.Parse<TestRecursiveMessage>(data65));
+
+            var parser63 = new JsonParser(new JsonParser.Settings(63));
+            Assert.Throws<InvalidProtocolBufferException>(() => parser63.Parse<TestRecursiveMessage>(data64));
+        }
+
+        [Test]
+        [TestCase("AQI")]
+        [TestCase("_-==")]
+        public void Bytes_InvalidBase64(string badBase64)
+        {
+            string json = "{ \"singleBytes\": \"" + badBase64 + "\" }";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        [TestCase("\"FOREIGN_BAR\"", ForeignEnum.ForeignBar)]
+        [TestCase("5", ForeignEnum.ForeignBar)]
+        [TestCase("100", (ForeignEnum)100)]
+        public void EnumValid(string value, ForeignEnum expectedValue)
+        {
+            string json = "{ \"singleForeignEnum\": " + value + " }";
+            var parsed = TestAllTypes.Parser.ParseJson(json);
+            Assert.AreEqual(new TestAllTypes { SingleForeignEnum = expectedValue }, parsed);
+        }
+
+        [Test]
+        [TestCase("\"NOT_A_VALID_VALUE\"")]
+        [TestCase("5.5")]
+        public void Enum_Invalid(string value)
+        {
+            string json = "{ \"singleForeignEnum\": " + value + " }";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        [Test]
+        public void OneofDuplicate_Invalid()
+        {
+            string json = "{ \"oneofString\": \"x\", \"oneofUint32\": 10 }";
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseJson(json));
+        }
+
+        /// <summary>
+        /// Various tests use strings which have quotes round them for parsing or as the result
+        /// of formatting, but without those quotes being specified in the tests (for the sake of readability).
+        /// This method simply returns the input, wrapped in double quotes.
+        /// </summary>
+        internal static string WrapInQuotes(string text)
+        {
+            return '"' + text + '"';
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/JsonTokenizerTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/JsonTokenizerTest.cs
new file mode 100644
index 0000000..527ab33
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/JsonTokenizerTest.cs
@@ -0,0 +1,408 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+using NUnit.Framework;
+using System;
+using System.IO;
+
+namespace Google.Protobuf
+{
+    public class JsonTokenizerTest
+    {
+        [Test]
+        public void EmptyObjectValue()
+        {
+            AssertTokens("{}", JsonToken.StartObject, JsonToken.EndObject);
+        }
+
+        [Test]
+        public void EmptyArrayValue()
+        {
+            AssertTokens("[]", JsonToken.StartArray, JsonToken.EndArray);
+        }
+
+        [Test]
+        [TestCase("foo", "foo")]
+        [TestCase("tab\\t", "tab\t")]
+        [TestCase("line\\nfeed", "line\nfeed")]
+        [TestCase("carriage\\rreturn", "carriage\rreturn")]
+        [TestCase("back\\bspace", "back\bspace")]
+        [TestCase("form\\ffeed", "form\ffeed")]
+        [TestCase("escaped\\/slash", "escaped/slash")]
+        [TestCase("escaped\\\\backslash", "escaped\\backslash")]
+        [TestCase("escaped\\\"quote", "escaped\"quote")]
+        [TestCase("foo {}[] bar", "foo {}[] bar")]
+        [TestCase("foo\\u09aFbar", "foo\u09afbar")] // Digits, upper hex, lower hex
+        [TestCase("ab\ud800\udc00cd", "ab\ud800\udc00cd")]
+        [TestCase("ab\\ud800\\udc00cd", "ab\ud800\udc00cd")]
+        public void StringValue(string json, string expectedValue)
+        {
+            AssertTokensNoReplacement("\"" + json + "\"", JsonToken.Value(expectedValue));
+        }
+
+        // Valid surrogate pairs, with mixed escaping. These test cases can't be expressed
+        // using TestCase as they have no valid UTF-8 representation.
+        // It's unclear exactly how we should handle a mixture of escaped or not: that can't
+        // come from UTF-8 text, but could come from a .NET string. For the moment,
+        // treat it as valid in the obvious way.
+        [Test]
+        public void MixedSurrogatePairs()
+        {
+            string expected = "\ud800\udc00";
+            AssertTokens("'\\ud800\udc00'", JsonToken.Value(expected));
+            AssertTokens("'\ud800\\udc00'", JsonToken.Value(expected));
+        }
+
+        [Test]
+        public void ObjectDepth()
+        {
+            string json = "{ \"foo\": { \"x\": 1, \"y\": [ 0 ] } }";
+            var tokenizer = JsonTokenizer.FromTextReader(new StringReader(json));
+            // If we had more tests like this, I'd introduce a helper method... but for one test, it's not worth it.
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.StartObject, tokenizer.Next());
+            Assert.AreEqual(1, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.Name("foo"), tokenizer.Next());
+            Assert.AreEqual(1, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.StartObject, tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.Name("x"), tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.Value(1), tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.Name("y"), tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.StartArray, tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth); // Depth hasn't changed in array
+            Assert.AreEqual(JsonToken.Value(0), tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.EndArray, tokenizer.Next());
+            Assert.AreEqual(2, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.EndObject, tokenizer.Next());
+            Assert.AreEqual(1, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.EndObject, tokenizer.Next());
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+            Assert.AreEqual(JsonToken.EndDocument, tokenizer.Next());
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+        }
+
+        [Test]
+        public void ObjectDepth_WithPushBack()
+        {
+            string json = "{}";
+            var tokenizer = JsonTokenizer.FromTextReader(new StringReader(json));
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+            var token = tokenizer.Next();
+            Assert.AreEqual(1, tokenizer.ObjectDepth);
+            // When we push back a "start object", we should effectively be back to the previous depth.
+            tokenizer.PushBack(token);
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+            // Read the same token again, and get back to depth 1
+            token = tokenizer.Next();
+            Assert.AreEqual(1, tokenizer.ObjectDepth);
+
+            // Now the same in reverse, with EndObject
+            token = tokenizer.Next();
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+            tokenizer.PushBack(token);
+            Assert.AreEqual(1, tokenizer.ObjectDepth);
+            tokenizer.Next();
+            Assert.AreEqual(0, tokenizer.ObjectDepth);
+        }
+
+        [Test]
+        [TestCase("embedded tab\t")]
+        [TestCase("embedded CR\r")]
+        [TestCase("embedded LF\n")]
+        [TestCase("embedded bell\u0007")]
+        [TestCase("bad escape\\a")]
+        [TestCase("incomplete escape\\")]
+        [TestCase("incomplete Unicode escape\\u000")]
+        [TestCase("invalid Unicode escape\\u000H")]
+        // Surrogate pair handling, both in raw .NET strings and escaped. We only need
+        // to detect this in strings, as non-ASCII characters anywhere other than in strings
+        // will already lead to parsing errors.
+        [TestCase("\\ud800")]
+        [TestCase("\\udc00")]
+        [TestCase("\\ud800x")]
+        [TestCase("\\udc00x")]
+        [TestCase("\\udc00\\ud800y")]
+        public void InvalidStringValue(string json)
+        {
+            AssertThrowsAfter("\"" + json + "\"");
+        }
+
+        // Tests for invalid strings that can't be expressed in attributes,
+        // as the constants can't be expressed as UTF-8 strings.
+        [Test]
+        public void InvalidSurrogatePairs()
+        {
+            AssertThrowsAfter("\"\ud800x\"");
+            AssertThrowsAfter("\"\udc00y\"");
+            AssertThrowsAfter("\"\udc00\ud800y\"");
+        }
+
+        [Test]
+        [TestCase("0", 0)]
+        [TestCase("-0", 0)] // We don't distinguish between positive and negative 0
+        [TestCase("1", 1)]
+        [TestCase("-1", -1)]
+        // From here on, assume leading sign is okay...
+        [TestCase("1.125", 1.125)]
+        [TestCase("1.0", 1)]
+        [TestCase("1e5", 100000)]
+        [TestCase("1e000000", 1)] // Weird, but not prohibited by the spec
+        [TestCase("1E5", 100000)]
+        [TestCase("1e+5", 100000)]
+        [TestCase("1E-5", 0.00001)]
+        [TestCase("123E-2", 1.23)]
+        [TestCase("123.45E3", 123450)]
+        [TestCase("   1   ", 1)]
+        public void NumberValue(string json, double expectedValue)
+        {
+            AssertTokens(json, JsonToken.Value(expectedValue));
+        }
+
+        [Test]
+        [TestCase("00")]
+        [TestCase(".5")]
+        [TestCase("1.")]
+        [TestCase("1e")]
+        [TestCase("1e-")]
+        [TestCase("--")]
+        [TestCase("--1")]
+        [TestCase("-1.7977e308")]
+        [TestCase("1.7977e308")]
+        public void InvalidNumberValue(string json)
+        {
+            AssertThrowsAfter(json);
+        }
+
+        [Test]
+        [TestCase("nul")]
+        [TestCase("nothing")]
+        [TestCase("truth")]
+        [TestCase("fALSEhood")]
+        public void InvalidLiterals(string json)
+        {
+            AssertThrowsAfter(json);
+        }
+
+        [Test]
+        public void NullValue()
+        {
+            AssertTokens("null", JsonToken.Null);
+        }
+
+        [Test]
+        public void TrueValue()
+        {
+            AssertTokens("true", JsonToken.True);
+        }
+
+        [Test]
+        public void FalseValue()
+        {
+            AssertTokens("false", JsonToken.False);
+        }
+
+        [Test]
+        public void SimpleObject()
+        {
+            AssertTokens("{'x': 'y'}",
+                JsonToken.StartObject, JsonToken.Name("x"), JsonToken.Value("y"), JsonToken.EndObject);
+        }
+        
+        [Test]
+        [TestCase("[10, 20", 3)]
+        [TestCase("[10,", 2)]
+        [TestCase("[10:20]", 2)]
+        [TestCase("[", 1)]
+        [TestCase("[,", 1)]
+        [TestCase("{", 1)]
+        [TestCase("{,", 1)]
+        [TestCase("{[", 1)]
+        [TestCase("{{", 1)]
+        [TestCase("{0", 1)]
+        [TestCase("{null", 1)]
+        [TestCase("{false", 1)]
+        [TestCase("{true", 1)]
+        [TestCase("}", 0)]
+        [TestCase("]", 0)]
+        [TestCase(",", 0)]
+        [TestCase("'foo' 'bar'", 1)]
+        [TestCase(":", 0)]
+        [TestCase("'foo", 0)] // Incomplete string
+        [TestCase("{ 'foo' }", 2)]
+        [TestCase("{ x:1", 1)] // Property names must be quoted
+        [TestCase("{]", 1)]
+        [TestCase("[}", 1)]
+        [TestCase("[1,", 2)]
+        [TestCase("{'x':0]", 3)]
+        [TestCase("{ 'foo': }", 2)]
+        [TestCase("{ 'foo':'bar', }", 3)]
+        public void InvalidStructure(string json, int expectedValidTokens)
+        {
+            // Note: we don't test that the earlier tokens are exactly as expected,
+            // partly because that's hard to parameterize.
+            var reader = new StringReader(json.Replace('\'', '"'));
+            var tokenizer = JsonTokenizer.FromTextReader(reader);
+            for (int i = 0; i < expectedValidTokens; i++)
+            {
+                Assert.IsNotNull(tokenizer.Next());
+            }
+            Assert.Throws<InvalidJsonException>(() => tokenizer.Next());
+        }
+
+        [Test]
+        public void ArrayMixedType()
+        {
+            AssertTokens("[1, 'foo', null, false, true, [2], {'x':'y' }]",
+                JsonToken.StartArray,
+                JsonToken.Value(1),
+                JsonToken.Value("foo"),
+                JsonToken.Null,
+                JsonToken.False,
+                JsonToken.True,
+                JsonToken.StartArray,
+                JsonToken.Value(2),
+                JsonToken.EndArray,
+                JsonToken.StartObject,
+                JsonToken.Name("x"),
+                JsonToken.Value("y"),
+                JsonToken.EndObject,
+                JsonToken.EndArray);
+        }
+
+        [Test]
+        public void ObjectMixedType()
+        {
+            AssertTokens(@"{'a': 1, 'b': 'bar', 'c': null, 'd': false, 'e': true, 
+                           'f': [2], 'g': {'x':'y' }}",
+                JsonToken.StartObject,
+                JsonToken.Name("a"),
+                JsonToken.Value(1),
+                JsonToken.Name("b"),
+                JsonToken.Value("bar"),
+                JsonToken.Name("c"),
+                JsonToken.Null,
+                JsonToken.Name("d"),
+                JsonToken.False,
+                JsonToken.Name("e"),
+                JsonToken.True,
+                JsonToken.Name("f"),
+                JsonToken.StartArray,
+                JsonToken.Value(2),
+                JsonToken.EndArray,
+                JsonToken.Name("g"),
+                JsonToken.StartObject,
+                JsonToken.Name("x"),
+                JsonToken.Value("y"),
+                JsonToken.EndObject,
+                JsonToken.EndObject);
+        }
+
+        [Test]
+        public void NextAfterEndDocumentThrows()
+        {
+            var tokenizer = JsonTokenizer.FromTextReader(new StringReader("null"));
+            Assert.AreEqual(JsonToken.Null, tokenizer.Next());
+            Assert.AreEqual(JsonToken.EndDocument, tokenizer.Next());
+            Assert.Throws<InvalidOperationException>(() => tokenizer.Next());
+        }
+
+        [Test]
+        public void CanPushBackEndDocument()
+        {
+            var tokenizer = JsonTokenizer.FromTextReader(new StringReader("null"));
+            Assert.AreEqual(JsonToken.Null, tokenizer.Next());
+            Assert.AreEqual(JsonToken.EndDocument, tokenizer.Next());
+            tokenizer.PushBack(JsonToken.EndDocument);
+            Assert.AreEqual(JsonToken.EndDocument, tokenizer.Next());
+            Assert.Throws<InvalidOperationException>(() => tokenizer.Next());
+        }
+       
+        /// <summary>
+        /// Asserts that the specified JSON is tokenized into the given sequence of tokens.
+        /// All apostrophes are first converted to double quotes, allowing any tests
+        /// that don't need to check actual apostrophe handling to use apostrophes in the JSON, avoiding
+        /// messy string literal escaping. The "end document" token is not specified in the list of 
+        /// expected tokens, but is implicit.
+        /// </summary>
+        private static void AssertTokens(string json, params JsonToken[] expectedTokens)
+        {
+            AssertTokensNoReplacement(json.Replace('\'', '"'), expectedTokens);
+        }
+
+        /// <summary>
+        /// Asserts that the specified JSON is tokenized into the given sequence of tokens.
+        /// Unlike <see cref="AssertTokens(string, JsonToken[])"/>, this does not perform any character
+        /// replacement on the specified JSON, and should be used when the text contains apostrophes which
+        /// are expected to be used *as* apostrophes. The "end document" token is not specified in the list of 
+        /// expected tokens, but is implicit.
+        /// </summary>
+        private static void AssertTokensNoReplacement(string json, params JsonToken[] expectedTokens)
+        {
+            var reader = new StringReader(json);
+            var tokenizer = JsonTokenizer.FromTextReader(reader);
+            for (int i = 0; i < expectedTokens.Length; i++)
+            {
+                var actualToken = tokenizer.Next();
+                if (actualToken == JsonToken.EndDocument)
+                {
+                    Assert.Fail("Expected {0} but reached end of token stream", expectedTokens[i]);
+                }
+                Assert.AreEqual(expectedTokens[i], actualToken);
+            }
+            var finalToken = tokenizer.Next();
+            if (finalToken != JsonToken.EndDocument)
+            {
+                Assert.Fail("Expected token stream to be exhausted; received {0}", finalToken);
+            }
+        }
+
+        private static void AssertThrowsAfter(string json, params JsonToken[] expectedTokens)
+        {
+            var reader = new StringReader(json);
+            var tokenizer = JsonTokenizer.FromTextReader(reader);
+            for (int i = 0; i < expectedTokens.Length; i++)
+            {
+                var actualToken = tokenizer.Next();
+                if (actualToken == JsonToken.EndDocument)
+                {
+                    Assert.Fail("Expected {0} but reached end of document", expectedTokens[i]);
+                }
+                Assert.AreEqual(expectedTokens[i], actualToken);
+            }
+            Assert.Throws<InvalidJsonException>(() => tokenizer.Next());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Program.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Program.cs
new file mode 100644
index 0000000..9078e59
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Program.cs
@@ -0,0 +1,47 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2017 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+using NUnitLite;
+using System.Reflection;
+
+// Note: this file wasn't in the actual 3.0, but is required due to build
+// system changes
+
+namespace Google.Protobuf.Test
+{
+    class Program
+    {
+        public static int Main(string[] args)
+        {
+            return new AutoRun(typeof(Program).GetTypeInfo().Assembly).Execute(args);
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs
new file mode 100644
index 0000000..52d5a67
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs
@@ -0,0 +1,259 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System.Linq;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+using UnitTest.Issues.TestProtos;
+
+namespace Google.Protobuf.Reflection
+{
+    /// <summary>
+    /// Tests for descriptors. (Not in its own namespace or broken up into individual classes as the
+    /// size doesn't warrant it. On the other hand, this makes me feel a bit dirty...)
+    /// </summary>
+    public class DescriptorsTest
+    {
+        [Test]
+        public void FileDescriptor()
+        {
+            FileDescriptor file = UnittestProto3Reflection.Descriptor;
+
+            Assert.AreEqual("google/protobuf/unittest_proto3.proto", file.Name);
+            Assert.AreEqual("protobuf_unittest", file.Package);
+
+            Assert.AreEqual("UnittestProto", file.Proto.Options.JavaOuterClassname);
+            Assert.AreEqual("google/protobuf/unittest_proto3.proto", file.Proto.Name);
+
+            // unittest.proto doesn't have any public imports, but unittest_import.proto does.
+            Assert.AreEqual(0, file.PublicDependencies.Count);
+            Assert.AreEqual(1, UnittestImportProto3Reflection.Descriptor.PublicDependencies.Count);
+            Assert.AreEqual(UnittestImportPublicProto3Reflection.Descriptor, UnittestImportProto3Reflection.Descriptor.PublicDependencies[0]);
+
+            Assert.AreEqual(1, file.Dependencies.Count);
+            Assert.AreEqual(UnittestImportProto3Reflection.Descriptor, file.Dependencies[0]);
+
+            MessageDescriptor messageType = TestAllTypes.Descriptor;
+            Assert.AreSame(typeof(TestAllTypes), messageType.ClrType);
+            Assert.AreSame(TestAllTypes.Parser, messageType.Parser);
+            Assert.AreEqual(messageType, file.MessageTypes[0]);
+            Assert.AreEqual(messageType, file.FindTypeByName<MessageDescriptor>("TestAllTypes"));
+            Assert.Null(file.FindTypeByName<MessageDescriptor>("NoSuchType"));
+            Assert.Null(file.FindTypeByName<MessageDescriptor>("protobuf_unittest.TestAllTypes"));
+            for (int i = 0; i < file.MessageTypes.Count; i++)
+            {
+                Assert.AreEqual(i, file.MessageTypes[i].Index);
+            }
+
+            Assert.AreEqual(file.EnumTypes[0], file.FindTypeByName<EnumDescriptor>("ForeignEnum"));
+            Assert.Null(file.FindTypeByName<EnumDescriptor>("NoSuchType"));
+            Assert.Null(file.FindTypeByName<EnumDescriptor>("protobuf_unittest.ForeignEnum"));
+            Assert.AreEqual(1, UnittestImportProto3Reflection.Descriptor.EnumTypes.Count);
+            Assert.AreEqual("ImportEnum", UnittestImportProto3Reflection.Descriptor.EnumTypes[0].Name);
+            for (int i = 0; i < file.EnumTypes.Count; i++)
+            {
+                Assert.AreEqual(i, file.EnumTypes[i].Index);
+            }
+
+            Assert.AreEqual(10, file.SerializedData[0]);
+        }
+
+        [Test]
+        public void MessageDescriptor()
+        {
+            MessageDescriptor messageType = TestAllTypes.Descriptor;
+            MessageDescriptor nestedType = TestAllTypes.Types.NestedMessage.Descriptor;
+
+            Assert.AreEqual("TestAllTypes", messageType.Name);
+            Assert.AreEqual("protobuf_unittest.TestAllTypes", messageType.FullName);
+            Assert.AreEqual(UnittestProto3Reflection.Descriptor, messageType.File);
+            Assert.IsNull(messageType.ContainingType);
+            Assert.IsNull(messageType.Proto.Options);
+
+            Assert.AreEqual("TestAllTypes", messageType.Name);
+
+            Assert.AreEqual("NestedMessage", nestedType.Name);
+            Assert.AreEqual("protobuf_unittest.TestAllTypes.NestedMessage", nestedType.FullName);
+            Assert.AreEqual(UnittestProto3Reflection.Descriptor, nestedType.File);
+            Assert.AreEqual(messageType, nestedType.ContainingType);
+
+            FieldDescriptor field = messageType.Fields.InDeclarationOrder()[0];
+            Assert.AreEqual("single_int32", field.Name);
+            Assert.AreEqual(field, messageType.FindDescriptor<FieldDescriptor>("single_int32"));
+            Assert.Null(messageType.FindDescriptor<FieldDescriptor>("no_such_field"));
+            Assert.AreEqual(field, messageType.FindFieldByNumber(1));
+            Assert.Null(messageType.FindFieldByNumber(571283));
+            var fieldsInDeclarationOrder = messageType.Fields.InDeclarationOrder();
+            for (int i = 0; i < fieldsInDeclarationOrder.Count; i++)
+            {
+                Assert.AreEqual(i, fieldsInDeclarationOrder[i].Index);
+            }
+
+            Assert.AreEqual(nestedType, messageType.NestedTypes[0]);
+            Assert.AreEqual(nestedType, messageType.FindDescriptor<MessageDescriptor>("NestedMessage"));
+            Assert.Null(messageType.FindDescriptor<MessageDescriptor>("NoSuchType"));
+            for (int i = 0; i < messageType.NestedTypes.Count; i++)
+            {
+                Assert.AreEqual(i, messageType.NestedTypes[i].Index);
+            }
+
+            Assert.AreEqual(messageType.EnumTypes[0], messageType.FindDescriptor<EnumDescriptor>("NestedEnum"));
+            Assert.Null(messageType.FindDescriptor<EnumDescriptor>("NoSuchType"));
+            for (int i = 0; i < messageType.EnumTypes.Count; i++)
+            {
+                Assert.AreEqual(i, messageType.EnumTypes[i].Index);
+            }
+        }
+
+        [Test]
+        public void FieldDescriptor()
+        {
+            MessageDescriptor messageType = TestAllTypes.Descriptor;
+            FieldDescriptor primitiveField = messageType.FindDescriptor<FieldDescriptor>("single_int32");
+            FieldDescriptor enumField = messageType.FindDescriptor<FieldDescriptor>("single_nested_enum");
+            FieldDescriptor messageField = messageType.FindDescriptor<FieldDescriptor>("single_foreign_message");
+
+            Assert.AreEqual("single_int32", primitiveField.Name);
+            Assert.AreEqual("protobuf_unittest.TestAllTypes.single_int32",
+                            primitiveField.FullName);
+            Assert.AreEqual(1, primitiveField.FieldNumber);
+            Assert.AreEqual(messageType, primitiveField.ContainingType);
+            Assert.AreEqual(UnittestProto3Reflection.Descriptor, primitiveField.File);
+            Assert.AreEqual(FieldType.Int32, primitiveField.FieldType);
+            Assert.IsNull(primitiveField.Proto.Options);
+            
+            Assert.AreEqual("single_nested_enum", enumField.Name);
+            Assert.AreEqual(FieldType.Enum, enumField.FieldType);
+            // Assert.AreEqual(TestAllTypes.Types.NestedEnum.DescriptorProtoFile, enumField.EnumType);
+
+            Assert.AreEqual("single_foreign_message", messageField.Name);
+            Assert.AreEqual(FieldType.Message, messageField.FieldType);
+            Assert.AreEqual(ForeignMessage.Descriptor, messageField.MessageType);
+        }
+
+        [Test]
+        public void FieldDescriptorLabel()
+        {
+            FieldDescriptor singleField =
+                TestAllTypes.Descriptor.FindDescriptor<FieldDescriptor>("single_int32");
+            FieldDescriptor repeatedField =
+                TestAllTypes.Descriptor.FindDescriptor<FieldDescriptor>("repeated_int32");
+
+            Assert.IsFalse(singleField.IsRepeated);
+            Assert.IsTrue(repeatedField.IsRepeated);
+        }
+
+        [Test]
+        public void EnumDescriptor()
+        {
+            // Note: this test is a bit different to the Java version because there's no static way of getting to the descriptor
+            EnumDescriptor enumType = UnittestProto3Reflection.Descriptor.FindTypeByName<EnumDescriptor>("ForeignEnum");
+            EnumDescriptor nestedType = TestAllTypes.Descriptor.FindDescriptor<EnumDescriptor>("NestedEnum");
+
+            Assert.AreEqual("ForeignEnum", enumType.Name);
+            Assert.AreEqual("protobuf_unittest.ForeignEnum", enumType.FullName);
+            Assert.AreEqual(UnittestProto3Reflection.Descriptor, enumType.File);
+            Assert.Null(enumType.ContainingType);
+            Assert.Null(enumType.Proto.Options);
+
+            Assert.AreEqual("NestedEnum", nestedType.Name);
+            Assert.AreEqual("protobuf_unittest.TestAllTypes.NestedEnum",
+                            nestedType.FullName);
+            Assert.AreEqual(UnittestProto3Reflection.Descriptor, nestedType.File);
+            Assert.AreEqual(TestAllTypes.Descriptor, nestedType.ContainingType);
+
+            EnumValueDescriptor value = enumType.FindValueByName("FOREIGN_FOO");
+            Assert.AreEqual(value, enumType.Values[1]);
+            Assert.AreEqual("FOREIGN_FOO", value.Name);
+            Assert.AreEqual(4, value.Number);
+            Assert.AreEqual((int) ForeignEnum.ForeignFoo, value.Number);
+            Assert.AreEqual(value, enumType.FindValueByNumber(4));
+            Assert.Null(enumType.FindValueByName("NO_SUCH_VALUE"));
+            for (int i = 0; i < enumType.Values.Count; i++)
+            {
+                Assert.AreEqual(i, enumType.Values[i].Index);
+            }
+        }
+
+        [Test]
+        public void OneofDescriptor()
+        {
+            OneofDescriptor descriptor = TestAllTypes.Descriptor.FindDescriptor<OneofDescriptor>("oneof_field");
+            Assert.AreEqual("oneof_field", descriptor.Name);
+            Assert.AreEqual("protobuf_unittest.TestAllTypes.oneof_field", descriptor.FullName);
+
+            var expectedFields = new[] {
+                TestAllTypes.OneofBytesFieldNumber,
+                TestAllTypes.OneofNestedMessageFieldNumber,
+                TestAllTypes.OneofStringFieldNumber,
+                TestAllTypes.OneofUint32FieldNumber }
+                .Select(fieldNumber => TestAllTypes.Descriptor.FindFieldByNumber(fieldNumber))
+                .ToList();
+            foreach (var field in expectedFields)
+            {
+                Assert.AreSame(descriptor, field.ContainingOneof);
+            }
+
+            CollectionAssert.AreEquivalent(expectedFields, descriptor.Fields);
+        }
+
+        [Test]
+        public void MapEntryMessageDescriptor()
+        {
+            var descriptor = MapWellKnownTypes.Descriptor.NestedTypes[0];
+            Assert.IsNull(descriptor.Parser);
+            Assert.IsNull(descriptor.ClrType);
+            Assert.IsNull(descriptor.Fields[1].Accessor);
+        }
+
+        // From TestFieldOrdering:
+        // string my_string = 11;
+        // int64 my_int = 1;
+        // float my_float = 101;
+        // NestedMessage single_nested_message = 200;
+        [Test]
+        public void FieldListOrderings()
+        { 
+            var fields = TestFieldOrderings.Descriptor.Fields;
+            Assert.AreEqual(new[] { 11, 1, 101, 200 }, fields.InDeclarationOrder().Select(x => x.FieldNumber));
+            Assert.AreEqual(new[] { 1, 11, 101, 200 }, fields.InFieldNumberOrder().Select(x => x.FieldNumber));
+        }
+
+
+        [Test]
+        public void DescriptorProtoFileDescriptor()
+        {
+            var descriptor = Google.Protobuf.Reflection.FileDescriptor.DescriptorProtoFileDescriptor;
+            Assert.AreEqual("google/protobuf/descriptor.proto", descriptor.Name);
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/FieldAccessTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/FieldAccessTest.cs
new file mode 100644
index 0000000..a488af3
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/FieldAccessTest.cs
@@ -0,0 +1,218 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+namespace Google.Protobuf.Reflection
+{
+    public class FieldAccessTest
+    {
+        [Test]
+        public void GetValue()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var fields = TestAllTypes.Descriptor.Fields;
+            Assert.AreEqual(message.SingleBool, fields[TestAllTypes.SingleBoolFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleBytes, fields[TestAllTypes.SingleBytesFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleDouble, fields[TestAllTypes.SingleDoubleFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleFixed32, fields[TestAllTypes.SingleFixed32FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleFixed64, fields[TestAllTypes.SingleFixed64FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleFloat, fields[TestAllTypes.SingleFloatFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleForeignEnum, fields[TestAllTypes.SingleForeignEnumFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleForeignMessage, fields[TestAllTypes.SingleForeignMessageFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleImportEnum, fields[TestAllTypes.SingleImportEnumFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleImportMessage, fields[TestAllTypes.SingleImportMessageFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleInt32, fields[TestAllTypes.SingleInt32FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleInt64, fields[TestAllTypes.SingleInt64FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleNestedEnum, fields[TestAllTypes.SingleNestedEnumFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleNestedMessage, fields[TestAllTypes.SingleNestedMessageFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SinglePublicImportMessage, fields[TestAllTypes.SinglePublicImportMessageFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleSint32, fields[TestAllTypes.SingleSint32FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleSint64, fields[TestAllTypes.SingleSint64FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleString, fields[TestAllTypes.SingleStringFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleSfixed32, fields[TestAllTypes.SingleSfixed32FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleSfixed64, fields[TestAllTypes.SingleSfixed64FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleUint32, fields[TestAllTypes.SingleUint32FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.SingleUint64, fields[TestAllTypes.SingleUint64FieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.OneofBytes, fields[TestAllTypes.OneofBytesFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.OneofString, fields[TestAllTypes.OneofStringFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.OneofNestedMessage, fields[TestAllTypes.OneofNestedMessageFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(message.OneofUint32, fields[TestAllTypes.OneofUint32FieldNumber].Accessor.GetValue(message));
+
+            // Just one example for repeated fields - they're all just returning the list
+            var list = (IList) fields[TestAllTypes.RepeatedInt32FieldNumber].Accessor.GetValue(message);
+            Assert.AreEqual(message.RepeatedInt32, list);
+            Assert.AreEqual(message.RepeatedInt32[0], list[0]); // Just in case there was any doubt...
+
+            // Just a single map field, for the same reason
+            var mapMessage = new TestMap { MapStringString = { { "key1", "value1" }, { "key2", "value2" } } };
+            fields = TestMap.Descriptor.Fields;
+            var dictionary = (IDictionary) fields[TestMap.MapStringStringFieldNumber].Accessor.GetValue(mapMessage);
+            Assert.AreEqual(mapMessage.MapStringString, dictionary);
+            Assert.AreEqual("value1", dictionary["key1"]);
+        }
+
+        [Test]
+        public void Clear()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var fields = TestAllTypes.Descriptor.Fields;
+            fields[TestAllTypes.SingleBoolFieldNumber].Accessor.Clear(message);
+            fields[TestAllTypes.SingleInt32FieldNumber].Accessor.Clear(message);
+            fields[TestAllTypes.SingleStringFieldNumber].Accessor.Clear(message);
+            fields[TestAllTypes.SingleBytesFieldNumber].Accessor.Clear(message);
+            fields[TestAllTypes.SingleForeignEnumFieldNumber].Accessor.Clear(message);
+            fields[TestAllTypes.SingleForeignMessageFieldNumber].Accessor.Clear(message);
+            fields[TestAllTypes.RepeatedDoubleFieldNumber].Accessor.Clear(message);
+
+            var expected = new TestAllTypes(SampleMessages.CreateFullTestAllTypes())
+            {
+                SingleBool = false,
+                SingleInt32 = 0,
+                SingleString = "",
+                SingleBytes = ByteString.Empty,
+                SingleForeignEnum = 0,
+                SingleForeignMessage = null,
+            };
+            expected.RepeatedDouble.Clear();
+
+            Assert.AreEqual(expected, message);
+
+            // Separately, maps.
+            var mapMessage = new TestMap { MapStringString = { { "key1", "value1" }, { "key2", "value2" } } };
+            fields = TestMap.Descriptor.Fields;
+            fields[TestMap.MapStringStringFieldNumber].Accessor.Clear(mapMessage);
+            Assert.AreEqual(0, mapMessage.MapStringString.Count);
+        }
+
+        [Test]
+        public void SetValue_SingleFields()
+        {
+            // Just a sample (primitives, messages, enums, strings, byte strings)
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var fields = TestAllTypes.Descriptor.Fields;
+            fields[TestAllTypes.SingleBoolFieldNumber].Accessor.SetValue(message, false);
+            fields[TestAllTypes.SingleInt32FieldNumber].Accessor.SetValue(message, 500);
+            fields[TestAllTypes.SingleStringFieldNumber].Accessor.SetValue(message, "It's a string");
+            fields[TestAllTypes.SingleBytesFieldNumber].Accessor.SetValue(message, ByteString.CopyFrom(99, 98, 97));
+            fields[TestAllTypes.SingleForeignEnumFieldNumber].Accessor.SetValue(message, ForeignEnum.ForeignFoo);
+            fields[TestAllTypes.SingleForeignMessageFieldNumber].Accessor.SetValue(message, new ForeignMessage { C = 12345 });
+            fields[TestAllTypes.SingleDoubleFieldNumber].Accessor.SetValue(message, 20150701.5);
+
+            var expected = new TestAllTypes(SampleMessages.CreateFullTestAllTypes())
+            {
+                SingleBool = false,
+                SingleInt32 = 500,
+                SingleString = "It's a string",
+                SingleBytes = ByteString.CopyFrom(99, 98, 97),
+                SingleForeignEnum = ForeignEnum.ForeignFoo,
+                SingleForeignMessage = new ForeignMessage { C = 12345 },
+                SingleDouble = 20150701.5
+            };
+
+            Assert.AreEqual(expected, message);
+        }
+
+        [Test]
+        public void SetValue_SingleFields_WrongType()
+        {
+            IMessage message = SampleMessages.CreateFullTestAllTypes();
+            var fields = message.Descriptor.Fields;
+            Assert.Throws<InvalidCastException>(() => fields[TestAllTypes.SingleBoolFieldNumber].Accessor.SetValue(message, "This isn't a bool"));
+        }
+
+        [Test]
+        public void SetValue_MapFields()
+        {
+            IMessage message = new TestMap();
+            var fields = message.Descriptor.Fields;
+            Assert.Throws<InvalidOperationException>(() => fields[TestMap.MapStringStringFieldNumber].Accessor.SetValue(message, new Dictionary<string, string>()));
+        }
+
+        [Test]
+        public void SetValue_RepeatedFields()
+        {
+            IMessage message = SampleMessages.CreateFullTestAllTypes();
+            var fields = message.Descriptor.Fields;
+            Assert.Throws<InvalidOperationException>(() => fields[TestAllTypes.RepeatedDoubleFieldNumber].Accessor.SetValue(message, new double[10]));
+        }
+
+        [Test]
+        public void GetValue_IncorrectType()
+        {
+            IMessage message = SampleMessages.CreateFullTestAllTypes();
+            var fields = message.Descriptor.Fields;
+            Assert.Throws<InvalidCastException>(() => fields[TestAllTypes.SingleBoolFieldNumber].Accessor.GetValue(new TestMap()));
+        }
+
+        [Test]
+        public void Oneof()
+        {
+            var message = new TestAllTypes();
+            var descriptor = TestAllTypes.Descriptor;
+            Assert.AreEqual(1, descriptor.Oneofs.Count);
+            var oneof = descriptor.Oneofs[0];
+            Assert.AreEqual("oneof_field", oneof.Name);
+            Assert.IsNull(oneof.Accessor.GetCaseFieldDescriptor(message));
+
+            message.OneofString = "foo";
+            Assert.AreSame(descriptor.Fields[TestAllTypes.OneofStringFieldNumber], oneof.Accessor.GetCaseFieldDescriptor(message));
+
+            message.OneofUint32 = 10;
+            Assert.AreSame(descriptor.Fields[TestAllTypes.OneofUint32FieldNumber], oneof.Accessor.GetCaseFieldDescriptor(message));
+
+            oneof.Accessor.Clear(message);
+            Assert.AreEqual(TestAllTypes.OneofFieldOneofCase.None, message.OneofFieldCase);
+        }
+
+        [Test]
+        public void FieldDescriptor_ByName()
+        {
+            var descriptor = TestAllTypes.Descriptor;
+            Assert.AreSame(
+                descriptor.Fields[TestAllTypes.SingleBoolFieldNumber],
+                descriptor.Fields["single_bool"]);
+        }
+
+        [Test]
+        public void FieldDescriptor_NotFound()
+        {
+            var descriptor = TestAllTypes.Descriptor;
+            Assert.Throws<KeyNotFoundException>(() => descriptor.Fields[999999].ToString());
+            Assert.Throws<KeyNotFoundException>(() => descriptor.Fields["not found"].ToString());
+        }        
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/TypeRegistryTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/TypeRegistryTest.cs
new file mode 100644
index 0000000..5be7ca2
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/Reflection/TypeRegistryTest.cs
@@ -0,0 +1,94 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using Google.Protobuf.TestProtos;
+using Google.Protobuf.WellKnownTypes;
+using NUnit.Framework;
+
+namespace Google.Protobuf.Reflection
+{
+    public class TypeRegistryTest
+    {
+        // Most of our tests use messages. Simple test that we really can use files...
+        [Test]
+        public void CreateWithFileDescriptor()
+        {
+            var registry = TypeRegistry.FromFiles(DurationReflection.Descriptor, StructReflection.Descriptor);
+            AssertDescriptorPresent(registry, Duration.Descriptor);
+            AssertDescriptorPresent(registry, ListValue.Descriptor);
+            AssertDescriptorAbsent(registry, Timestamp.Descriptor);
+        }
+
+        [Test]
+        public void TypesFromSameFile()
+        {
+            // Just for kicks, let's start with a nested type
+            var registry = TypeRegistry.FromMessages(TestAllTypes.Types.NestedMessage.Descriptor);
+            // Top-level...
+            AssertDescriptorPresent(registry, TestFieldOrderings.Descriptor);
+            // ... and nested (not the same as the original NestedMessage!)
+            AssertDescriptorPresent(registry, TestFieldOrderings.Types.NestedMessage.Descriptor);
+        }
+
+        [Test]
+        public void DependenciesAreIncluded()
+        {
+            var registry = TypeRegistry.FromMessages(TestAllTypes.Descriptor);
+            // Direct dependencies
+            AssertDescriptorPresent(registry, ImportMessage.Descriptor);
+            // Public dependencies
+            AssertDescriptorPresent(registry, PublicImportMessage.Descriptor);
+        }
+
+        [Test]
+        public void DuplicateFiles()
+        {
+            // Duplicates via dependencies and simply via repetition
+            var registry = TypeRegistry.FromFiles(
+                UnittestProto3Reflection.Descriptor, UnittestImportProto3Reflection.Descriptor,
+                TimestampReflection.Descriptor, TimestampReflection.Descriptor);
+            AssertDescriptorPresent(registry, TestAllTypes.Descriptor);
+            AssertDescriptorPresent(registry, ImportMessage.Descriptor);
+            AssertDescriptorPresent(registry, Timestamp.Descriptor);
+        }
+
+        private static void AssertDescriptorPresent(TypeRegistry registry, MessageDescriptor descriptor)
+        {
+            Assert.AreSame(descriptor, registry.Find(descriptor.FullName));
+        }
+
+        private static void AssertDescriptorAbsent(TypeRegistry registry, MessageDescriptor descriptor)
+        {
+            Assert.IsNull(registry.Find(descriptor.FullName));
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/SampleEnum.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/SampleEnum.cs
new file mode 100644
index 0000000..77447af
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/SampleEnum.cs
@@ -0,0 +1,42 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+    
+namespace Google.Protobuf
+{
+    // Just a sample enum with positive and negative values to be used in tests.
+    internal enum SampleEnum
+    {
+        NegativeValue = -2,
+        None = 0,
+        PositiveValue = 3
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/SampleMessages.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/SampleMessages.cs
new file mode 100644
index 0000000..ffa4e2a
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/SampleMessages.cs
@@ -0,0 +1,99 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using Google.Protobuf.TestProtos;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Helper methods to create sample instances of types generated from unit test messages.
+    /// </summary>
+    public class SampleMessages
+    {
+        /// <summary>
+        /// Creates a new sample TestAllTypes message with all fields populated.
+        /// The "oneof" field is populated with the string property (OneofString).
+        /// </summary>
+        public static TestAllTypes CreateFullTestAllTypes()
+        {
+            return new TestAllTypes
+            {
+                SingleBool = true,
+                SingleBytes = ByteString.CopyFrom(1, 2, 3, 4),
+                SingleDouble = 23.5,
+                SingleFixed32 = 23,
+                SingleFixed64 = 1234567890123,
+                SingleFloat = 12.25f,
+                SingleForeignEnum = ForeignEnum.ForeignBar,
+                SingleForeignMessage = new ForeignMessage { C = 10 },
+                SingleImportEnum = ImportEnum.ImportBaz,
+                SingleImportMessage = new ImportMessage { D = 20 },
+                SingleInt32 = 100,
+                SingleInt64 = 3210987654321,
+                SingleNestedEnum = TestAllTypes.Types.NestedEnum.Foo,
+                SingleNestedMessage = new TestAllTypes.Types.NestedMessage { Bb = 35 },
+                SinglePublicImportMessage = new PublicImportMessage { E = 54 },
+                SingleSfixed32 = -123,
+                SingleSfixed64 = -12345678901234,
+                SingleSint32 = -456,
+                SingleSint64 = -12345678901235,
+                SingleString = "test",
+                SingleUint32 = UInt32.MaxValue,
+                SingleUint64 = UInt64.MaxValue,
+                RepeatedBool = { true, false },
+                RepeatedBytes = { ByteString.CopyFrom(1, 2, 3, 4), ByteString.CopyFrom(5, 6), ByteString.CopyFrom(new byte[1000]) },
+                RepeatedDouble = { -12.25, 23.5 },
+                RepeatedFixed32 = { UInt32.MaxValue, 23 },
+                RepeatedFixed64 = { UInt64.MaxValue, 1234567890123 },
+                RepeatedFloat = { 100f, 12.25f },
+                RepeatedForeignEnum = { ForeignEnum.ForeignFoo, ForeignEnum.ForeignBar },
+                RepeatedForeignMessage = { new ForeignMessage(), new ForeignMessage { C = 10 } },
+                RepeatedImportEnum = { ImportEnum.ImportBaz, ImportEnum.Unspecified },
+                RepeatedImportMessage = { new ImportMessage { D = 20 }, new ImportMessage { D = 25 } },
+                RepeatedInt32 = { 100, 200 },
+                RepeatedInt64 = { 3210987654321, Int64.MaxValue },
+                RepeatedNestedEnum = { TestAllTypes.Types.NestedEnum.Foo, TestAllTypes.Types.NestedEnum.Neg },
+                RepeatedNestedMessage = { new TestAllTypes.Types.NestedMessage { Bb = 35 }, new TestAllTypes.Types.NestedMessage { Bb = 10 } },
+                RepeatedPublicImportMessage = { new PublicImportMessage { E = 54 }, new PublicImportMessage { E = -1 } },
+                RepeatedSfixed32 = { -123, 123 },
+                RepeatedSfixed64 = { -12345678901234, 12345678901234 },
+                RepeatedSint32 = { -456, 100 },
+                RepeatedSint64 = { -12345678901235, 123 },
+                RepeatedString = { "foo", "bar" },
+                RepeatedUint32 = { UInt32.MaxValue, UInt32.MinValue },
+                RepeatedUint64 = { UInt64.MaxValue, UInt32.MinValue },
+                OneofString = "Oneof string"
+            };
+        }
+    }
+}
\ No newline at end of file
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/TestCornerCases.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/TestCornerCases.cs
new file mode 100644
index 0000000..248f5fa
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/TestCornerCases.cs
@@ -0,0 +1,62 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+    
+using UnitTest.Issues.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class TestCornerCases
+    {
+        [Test]
+        public void TestRoundTripNegativeEnums()
+        {
+            NegativeEnumMessage msg = new NegativeEnumMessage
+            {
+                Value = NegativeEnum.MinusOne,
+                Values = { NegativeEnum.Zero, NegativeEnum.MinusOne, NegativeEnum.FiveBelow },
+                PackedValues = { NegativeEnum.Zero, NegativeEnum.MinusOne, NegativeEnum.FiveBelow }
+            };
+
+            Assert.AreEqual(58, msg.CalculateSize());
+
+            byte[] bytes = new byte[58];
+            CodedOutputStream output = new CodedOutputStream(bytes);
+
+            msg.WriteTo(output);
+            Assert.AreEqual(0, output.SpaceLeft);
+
+            NegativeEnumMessage copy = NegativeEnumMessage.Parser.ParseFrom(bytes);
+            Assert.AreEqual(msg, copy);
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/TestProtos/ForeignMessagePartial.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/TestProtos/ForeignMessagePartial.cs
new file mode 100644
index 0000000..5663a69
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/TestProtos/ForeignMessagePartial.cs
@@ -0,0 +1,45 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2016 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+namespace Google.Protobuf.TestProtos
+{
+    /// <summary>
+    /// A message with custom diagnostics (to test that they work).
+    /// </summary>
+    public partial class ForeignMessage : ICustomDiagnosticMessage
+    {
+        public string ToDiagnosticString()
+        {
+            return $"{{ \"c\": {C}, \"@cInHex\": \"{C:x}\" }}";
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/AnyTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/AnyTest.cs
new file mode 100644
index 0000000..4aecc99
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/AnyTest.cs
@@ -0,0 +1,116 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf.WellKnownTypes
+{
+    public class AnyTest
+    {
+        [Test]
+        public void Pack()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message);
+            Assert.AreEqual("type.googleapis.com/protobuf_unittest.TestAllTypes", any.TypeUrl);
+            Assert.AreEqual(message.CalculateSize(), any.Value.Length);
+        }
+
+        [Test]
+        public void Pack_WithCustomPrefix()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message, "foo.bar/baz");
+            Assert.AreEqual("foo.bar/baz/protobuf_unittest.TestAllTypes", any.TypeUrl);
+            Assert.AreEqual(message.CalculateSize(), any.Value.Length);
+        }
+
+        [Test]
+        public void Pack_WithCustomPrefixTrailingSlash()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message, "foo.bar/baz/");
+            Assert.AreEqual("foo.bar/baz/protobuf_unittest.TestAllTypes", any.TypeUrl);
+            Assert.AreEqual(message.CalculateSize(), any.Value.Length);
+        }
+
+        [Test]
+        public void Unpack_WrongType()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message);
+            Assert.Throws<InvalidProtocolBufferException>(() => any.Unpack<TestOneof>());
+        }
+
+        [Test]
+        public void Unpack_Success()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message);
+            var unpacked = any.Unpack<TestAllTypes>();
+            Assert.AreEqual(message, unpacked);
+        }
+
+        [Test]
+        public void Unpack_CustomPrefix_Success()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message, "foo.bar/baz");
+            var unpacked = any.Unpack<TestAllTypes>();
+            Assert.AreEqual(message, unpacked);
+        }
+
+        [Test]
+        public void ToString_WithValues()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message);
+            var text = any.ToString();
+            Assert.That(text, Does.Contain("\"@value\": \"" + message.ToByteString().ToBase64() + "\""));
+        }
+
+        [Test]
+        public void ToString_Empty()
+        {
+            var any = new Any();
+            Assert.AreEqual("{ \"@type\": \"\", \"@value\": \"\" }", any.ToString());
+        }
+
+        [Test]
+        public void ToString_MessageContainingAny()
+        {
+            var message = new TestWellKnownTypes { AnyField = new Any() };
+            Assert.AreEqual("{ \"anyField\": { \"@type\": \"\", \"@value\": \"\" } }", message.ToString());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/DurationTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/DurationTest.cs
new file mode 100644
index 0000000..141faf8
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/DurationTest.cs
@@ -0,0 +1,132 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using NUnit.Framework;
+using System;
+
+namespace Google.Protobuf.WellKnownTypes
+{
+    public class DurationTest
+    {
+        [Test]
+        public void ToTimeSpan()
+        {
+            Assert.AreEqual(TimeSpan.FromSeconds(1), new Duration { Seconds = 1 }.ToTimeSpan());
+            Assert.AreEqual(TimeSpan.FromSeconds(-1), new Duration { Seconds = -1 }.ToTimeSpan());
+            Assert.AreEqual(TimeSpan.FromMilliseconds(1), new Duration { Nanos = 1000000 }.ToTimeSpan());
+            Assert.AreEqual(TimeSpan.FromMilliseconds(-1), new Duration { Nanos = -1000000 }.ToTimeSpan());
+            Assert.AreEqual(TimeSpan.FromTicks(1), new Duration { Nanos = 100 }.ToTimeSpan());
+            Assert.AreEqual(TimeSpan.FromTicks(-1), new Duration { Nanos = -100 }.ToTimeSpan());
+
+            // Rounding is towards 0
+            Assert.AreEqual(TimeSpan.FromTicks(2), new Duration { Nanos = 250 }.ToTimeSpan());
+            Assert.AreEqual(TimeSpan.FromTicks(-2), new Duration { Nanos = -250 }.ToTimeSpan());
+        }
+
+        [Test]
+        public void Addition()
+        {
+            Assert.AreEqual(new Duration { Seconds = 2, Nanos = 100000000 },
+                new Duration { Seconds = 1, Nanos = 600000000 } + new Duration { Nanos = 500000000 });
+            Assert.AreEqual(new Duration { Seconds = -2, Nanos = -100000000 },
+                new Duration { Seconds = -1, Nanos = -600000000 } + new Duration { Nanos = -500000000 });
+            Assert.AreEqual(new Duration { Seconds = 1, Nanos = 100000000 },
+                new Duration { Seconds = 1, Nanos = 600000000 } + new Duration { Nanos = -500000000 });
+
+            // Non-normalized durations, or non-normalized intermediate results
+            Assert.AreEqual(new Duration { Seconds = 1 },
+                new Duration { Seconds = 1, Nanos = -500000000 } + new Duration { Nanos = 500000000 });
+
+            Assert.AreEqual(new Duration { Nanos = -900000000 },
+                new Duration { Seconds = -1, Nanos = -100000000 } + new Duration { Nanos = 200000000 });
+            Assert.AreEqual(new Duration { Nanos = 900000000 },
+                new Duration { Seconds = 1, Nanos = 100000000 } + new Duration { Nanos = -200000000 });
+        }
+
+        [Test]
+        public void Subtraction()
+        {
+            Assert.AreEqual(new Duration { Seconds = 1, Nanos = 100000000 },
+                new Duration { Seconds = 1, Nanos = 600000000 } - new Duration { Nanos = 500000000 });
+            Assert.AreEqual(new Duration { Seconds = -1, Nanos = -100000000 },
+                new Duration { Seconds = -1, Nanos = -600000000 } - new Duration { Nanos = -500000000 });
+            Assert.AreEqual(new Duration { Seconds = 2, Nanos = 100000000 },
+                new Duration { Seconds = 1, Nanos = 600000000 } - new Duration { Nanos = -500000000 });
+
+            // Non-normalized durations
+            Assert.AreEqual(new Duration(),
+                new Duration { Seconds = 1, Nanos = -500000000 } - new Duration { Nanos = 500000000 });
+            Assert.AreEqual(new Duration { Seconds = 1 },
+                new Duration { Nanos = 2000000000 } - new Duration { Nanos = 1000000000 });
+        }
+
+        [Test]
+        public void FromTimeSpan()
+        {
+            Assert.AreEqual(new Duration { Seconds = 1 }, Duration.FromTimeSpan(TimeSpan.FromSeconds(1)));
+            Assert.AreEqual(new Duration { Nanos = Duration.NanosecondsPerTick }, Duration.FromTimeSpan(TimeSpan.FromTicks(1)));
+        }
+
+        [Test]
+        [TestCase(0, Duration.MaxNanoseconds + 1)]
+        [TestCase(0, Duration.MinNanoseconds - 1)]
+        [TestCase(Duration.MinSeconds - 1, 0)]
+        [TestCase(Duration.MaxSeconds + 1, 0)]
+        [TestCase(1, -1)]
+        [TestCase(-1, 1)]
+        public void ToTimeSpan_Invalid(long seconds, int nanoseconds)
+        {
+            var duration = new Duration { Seconds = seconds, Nanos = nanoseconds };
+            Assert.Throws<InvalidOperationException>(() => duration.ToTimeSpan());
+        }
+
+        [Test]
+        [TestCase(0, Duration.MaxNanoseconds)]
+        [TestCase(0, Duration.MinNanoseconds)]
+        [TestCase(Duration.MinSeconds, Duration.MinNanoseconds)]
+        [TestCase(Duration.MaxSeconds, Duration.MaxNanoseconds)]
+        public void ToTimeSpan_Valid(long seconds, int nanoseconds)
+        {
+            // Only testing that these values don't throw, unlike their similar tests in ToTimeSpan_Invalid
+            var duration = new Duration { Seconds = seconds, Nanos = nanoseconds };
+            duration.ToTimeSpan();
+        }
+
+        [Test]
+        public void ToString_NonNormalized()
+        {
+            // Just a single example should be sufficient...
+            var duration = new Duration { Seconds = 1, Nanos = -1 };
+            Assert.AreEqual("{ \"@warning\": \"Invalid Duration\", \"seconds\": \"1\", \"nanos\": -1 }", duration.ToString());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/FieldMaskTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/FieldMaskTest.cs
new file mode 100644
index 0000000..1d9908b
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/FieldMaskTest.cs
@@ -0,0 +1,62 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2016 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+
+using NUnit.Framework;
+
+namespace Google.Protobuf.WellKnownTypes
+{
+    public class FieldMaskTest
+    {
+        [Test]
+        [TestCase("foo__bar")]
+        [TestCase("foo_3_ar")]
+        [TestCase("fooBar")]
+        public void ToString_Invalid(string input)
+        {
+            var mask = new FieldMask { Paths = { input } };
+            var text = mask.ToString();
+            // More specific test below
+            Assert.That(text, Does.Contain("@warning"));
+            Assert.That(text, Does.Contain(input));
+        }
+
+        [Test]
+        public void ToString_Invalid_Precise()
+        {
+            var mask = new FieldMask { Paths = { "x", "foo__bar", @"x\y" } };
+            Assert.AreEqual(
+                "{ \"@warning\": \"Invalid FieldMask\", \"paths\": [ \"x\", \"foo__bar\", \"x\\\\y\" ] }",
+                mask.ToString());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/TimestampTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/TimestampTest.cs
new file mode 100644
index 0000000..9ecd24c
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/TimestampTest.cs
@@ -0,0 +1,115 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using NUnit.Framework;
+using System;
+
+namespace Google.Protobuf.WellKnownTypes
+{
+    public class TimestampTest
+    {
+        [Test]
+        public void FromAndToDateTime()
+        {
+            DateTime utcMin = DateTime.SpecifyKind(DateTime.MinValue, DateTimeKind.Utc);
+            DateTime utcMax = DateTime.SpecifyKind(DateTime.MaxValue, DateTimeKind.Utc);
+            AssertRoundtrip(new Timestamp { Seconds = -62135596800 }, utcMin);
+            AssertRoundtrip(new Timestamp { Seconds = 253402300799, Nanos = 999999900 }, utcMax);
+            AssertRoundtrip(new Timestamp(), new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc));
+            AssertRoundtrip(new Timestamp { Nanos = 1000000}, new DateTime(1970, 1, 1, 0, 0, 0, 1, DateTimeKind.Utc));
+            AssertRoundtrip(new Timestamp { Seconds = -1, Nanos = 999000000 }, new DateTime(1969, 12, 31, 23, 59, 59, 999, DateTimeKind.Utc));
+            AssertRoundtrip(new Timestamp { Seconds = 3600 }, new DateTime(1970, 1, 1, 1, 0, 0, DateTimeKind.Utc));
+            AssertRoundtrip(new Timestamp { Seconds = -3600 }, new DateTime(1969, 12, 31, 23, 0, 0, DateTimeKind.Utc));
+        }
+
+        [Test]
+        public void ToDateTimeTruncation()
+        {
+            var t1 = new Timestamp { Seconds = 1, Nanos = 1000000 + Duration.NanosecondsPerTick - 1 };
+            Assert.AreEqual(new DateTime(1970, 1, 1, 0, 0, 1, DateTimeKind.Utc).AddMilliseconds(1), t1.ToDateTime());
+
+            var t2 = new Timestamp { Seconds = -1, Nanos = 1000000 + Duration.NanosecondsPerTick - 1 };
+            Assert.AreEqual(new DateTime(1969, 12, 31, 23, 59, 59).AddMilliseconds(1), t2.ToDateTime());
+        }
+
+        [Test]
+        [TestCase(Timestamp.UnixSecondsAtBclMinValue - 1, Timestamp.MaxNanos)]
+        [TestCase(Timestamp.UnixSecondsAtBclMaxValue + 1, 0)]
+        [TestCase(0, -1)]
+        [TestCase(0, Timestamp.MaxNanos + 1)]
+        public void ToDateTime_OutOfRange(long seconds, int nanoseconds)
+        {
+            var value = new Timestamp { Seconds = seconds, Nanos = nanoseconds };
+            Assert.Throws<InvalidOperationException>(() => value.ToDateTime());
+        }
+
+        // 1ns larger or smaller than the above values
+        [Test]
+        [TestCase(Timestamp.UnixSecondsAtBclMinValue, 0)]
+        [TestCase(Timestamp.UnixSecondsAtBclMaxValue, Timestamp.MaxNanos)]
+        [TestCase(0, 0)]
+        [TestCase(0, Timestamp.MaxNanos)]
+        public void ToDateTime_ValidBoundaries(long seconds, int nanoseconds)
+        {
+            var value = new Timestamp { Seconds = seconds, Nanos = nanoseconds };
+            value.ToDateTime();
+        }
+
+        private static void AssertRoundtrip(Timestamp timestamp, DateTime dateTime)
+        {
+            Assert.AreEqual(timestamp, Timestamp.FromDateTime(dateTime));
+            Assert.AreEqual(dateTime, timestamp.ToDateTime());
+            Assert.AreEqual(DateTimeKind.Utc, timestamp.ToDateTime().Kind);
+        }
+
+        [Test]
+        public void Arithmetic()
+        {
+            Timestamp t1 = new Timestamp { Seconds = 10000, Nanos = 5000 };
+            Timestamp t2 = new Timestamp { Seconds = 8000, Nanos = 10000 };
+            Duration difference = new Duration { Seconds = 1999, Nanos = Duration.NanosecondsPerSecond - 5000 };
+            Assert.AreEqual(difference, t1 - t2);
+            Assert.AreEqual(-difference, t2 - t1);
+            
+            Assert.AreEqual(t1, t2 + difference);
+            Assert.AreEqual(t2, t1 - difference);
+        }
+
+        [Test]
+        public void ToString_NonNormalized()
+        {
+            // Just a single example should be sufficient...
+            var duration = new Timestamp { Seconds = 1, Nanos = -1 };
+            Assert.AreEqual("{ \"@warning\": \"Invalid Timestamp\", \"seconds\": \"1\", \"nanos\": -1 }", duration.ToString());
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/WrappersTest.cs b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/WrappersTest.cs
new file mode 100644
index 0000000..5b7185d
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/src/Google.Protobuf.Test/WellKnownTypes/WrappersTest.cs
@@ -0,0 +1,421 @@
+﻿#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2015 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+using System.Collections;
+using System.IO;
+
+namespace Google.Protobuf.WellKnownTypes
+{
+    public class WrappersTest
+    {
+        [Test]
+        public void NullIsDefault()
+        {
+            var message = new TestWellKnownTypes();
+            Assert.IsNull(message.StringField);
+            Assert.IsNull(message.BytesField);
+            Assert.IsNull(message.BoolField);
+            Assert.IsNull(message.FloatField);
+            Assert.IsNull(message.DoubleField);
+            Assert.IsNull(message.Int32Field);
+            Assert.IsNull(message.Int64Field);
+            Assert.IsNull(message.Uint32Field);
+            Assert.IsNull(message.Uint64Field);
+        }
+
+        [Test]
+        public void NonDefaultSingleValues()
+        {
+            var message = new TestWellKnownTypes
+            {
+                StringField = "x",
+                BytesField = ByteString.CopyFrom(1, 2, 3),
+                BoolField = true,
+                FloatField = 12.5f,
+                DoubleField = 12.25d,
+                Int32Field = 1,
+                Int64Field = 2,
+                Uint32Field = 3,
+                Uint64Field = 4
+            };
+
+            var bytes = message.ToByteArray();
+            var parsed = TestWellKnownTypes.Parser.ParseFrom(bytes);
+
+            Assert.AreEqual("x", parsed.StringField);
+            Assert.AreEqual(ByteString.CopyFrom(1, 2, 3), parsed.BytesField);
+            Assert.AreEqual(true, parsed.BoolField);
+            Assert.AreEqual(12.5f, parsed.FloatField);
+            Assert.AreEqual(12.25d, parsed.DoubleField);
+            Assert.AreEqual(1, parsed.Int32Field);
+            Assert.AreEqual(2L, parsed.Int64Field);
+            Assert.AreEqual(3U, parsed.Uint32Field);
+            Assert.AreEqual(4UL, parsed.Uint64Field);
+        }
+
+        [Test]
+        public void NonNullDefaultIsPreservedThroughSerialization()
+        {
+            var message = new TestWellKnownTypes
+            {
+                StringField = "",
+                BytesField = ByteString.Empty,
+                BoolField = false,
+                FloatField = 0f,
+                DoubleField = 0d,
+                Int32Field = 0,
+                Int64Field = 0,
+                Uint32Field = 0,
+                Uint64Field = 0
+            };
+
+            var bytes = message.ToByteArray();
+            var parsed = TestWellKnownTypes.Parser.ParseFrom(bytes);
+
+            Assert.AreEqual("", parsed.StringField);
+            Assert.AreEqual(ByteString.Empty, parsed.BytesField);
+            Assert.AreEqual(false, parsed.BoolField);
+            Assert.AreEqual(0f, parsed.FloatField);
+            Assert.AreEqual(0d, parsed.DoubleField);
+            Assert.AreEqual(0, parsed.Int32Field);
+            Assert.AreEqual(0L, parsed.Int64Field);
+            Assert.AreEqual(0U, parsed.Uint32Field);
+            Assert.AreEqual(0UL, parsed.Uint64Field);
+        }
+
+        [Test]
+        public void RepeatedWrappersProhibitNullItems()
+        {
+            var message = new RepeatedWellKnownTypes();
+            Assert.Throws<ArgumentNullException>(() => message.BoolField.Add((bool?) null));
+            Assert.Throws<ArgumentNullException>(() => message.Int32Field.Add((int?) null));
+            Assert.Throws<ArgumentNullException>(() => message.StringField.Add((string) null));
+            Assert.Throws<ArgumentNullException>(() => message.BytesField.Add((ByteString) null));
+        }
+
+        [Test]
+        public void RepeatedWrappersSerializeDeserialize()
+        {
+            var message = new RepeatedWellKnownTypes
+            {
+                BoolField = { true, false },
+                BytesField = { ByteString.CopyFrom(1, 2, 3), ByteString.CopyFrom(4, 5, 6), ByteString.Empty },
+                DoubleField = { 12.5, -1.5, 0d },
+                FloatField = { 123.25f, -20f, 0f },
+                Int32Field = { int.MaxValue, int.MinValue, 0 },
+                Int64Field = { long.MaxValue, long.MinValue, 0L },                
+                StringField = { "First", "Second", "" },
+                Uint32Field = { uint.MaxValue, uint.MinValue, 0U },
+                Uint64Field = { ulong.MaxValue, ulong.MinValue, 0UL },
+            };
+            var bytes = message.ToByteArray();
+            var parsed = RepeatedWellKnownTypes.Parser.ParseFrom(bytes);
+
+            Assert.AreEqual(message, parsed);
+            // Just to test a single value for sanity...
+            Assert.AreEqual("Second", message.StringField[1]);
+        }
+
+        [Test]
+        public void RepeatedWrappersBinaryFormat()
+        {
+            // At one point we accidentally used a packed format for repeated wrappers, which is wrong (and weird).
+            // This test is just to prove that we use the right format.
+
+            var rawOutput = new MemoryStream();
+            var output = new CodedOutputStream(rawOutput);
+            // Write a value of 5
+            output.WriteTag(RepeatedWellKnownTypes.Int32FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(2);
+            output.WriteTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Varint);
+            output.WriteInt32(5);
+            // Write a value of 0 (empty message)
+            output.WriteTag(RepeatedWellKnownTypes.Int32FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            output.WriteLength(0);
+            output.Flush();
+            var expectedBytes = rawOutput.ToArray();
+
+            var message = new RepeatedWellKnownTypes { Int32Field = { 5, 0 } };
+            var actualBytes = message.ToByteArray();
+            Assert.AreEqual(expectedBytes, actualBytes);
+        }
+
+        [Test]
+        public void MapWrappersSerializeDeserialize()
+        {
+            // Note: no null values here, as they are prohibited in map fields
+            // (despite being representable).
+            var message = new MapWellKnownTypes
+            {
+                BoolField = { { 10, false }, { 20, true } },
+                BytesField = {
+                    { -1, ByteString.CopyFrom(1, 2, 3) },
+                    { 10, ByteString.CopyFrom(4, 5, 6) },
+                    { 1000, ByteString.Empty },
+                },
+                DoubleField = { { 1, 12.5 }, { 10, -1.5 }, { 20, 0d } },
+                FloatField = { { 2, 123.25f }, { 3, -20f }, { 4, 0f } },
+                Int32Field = { { 5, int.MaxValue }, { 6, int.MinValue }, { 7, 0 } },
+                Int64Field = { { 8, long.MaxValue }, { 9, long.MinValue }, { 10, 0L } },
+                StringField = { { 11, "First" }, { 12, "Second" }, { 13, "" } },
+                Uint32Field = { { 15, uint.MaxValue }, { 16, uint.MinValue }, { 17, 0U } },
+                Uint64Field = { { 18, ulong.MaxValue }, { 19, ulong.MinValue }, { 20, 0UL } },
+            };
+
+            var bytes = message.ToByteArray();
+            var parsed = MapWellKnownTypes.Parser.ParseFrom(bytes);
+
+            Assert.AreEqual(message, parsed);
+            // Just to test a single value for sanity...
+            Assert.AreEqual("Second", message.StringField[12]);
+        }
+
+        [Test]
+        public void Reflection_SingleValues()
+        {
+            var message = new TestWellKnownTypes
+            {
+                StringField = "x",
+                BytesField = ByteString.CopyFrom(1, 2, 3),
+                BoolField = true,
+                FloatField = 12.5f,
+                DoubleField = 12.25d,
+                Int32Field = 1,
+                Int64Field = 2,
+                Uint32Field = 3,
+                Uint64Field = 4
+            };
+            var fields = TestWellKnownTypes.Descriptor.Fields;
+
+            Assert.AreEqual("x", fields[TestWellKnownTypes.StringFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(ByteString.CopyFrom(1, 2, 3), fields[TestWellKnownTypes.BytesFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(true, fields[TestWellKnownTypes.BoolFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(12.5f, fields[TestWellKnownTypes.FloatFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(12.25d, fields[TestWellKnownTypes.DoubleFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(1, fields[TestWellKnownTypes.Int32FieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(2L, fields[TestWellKnownTypes.Int64FieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(3U, fields[TestWellKnownTypes.Uint32FieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(4UL, fields[TestWellKnownTypes.Uint64FieldFieldNumber].Accessor.GetValue(message));
+
+            // And a couple of null fields...
+            message.StringField = null;
+            message.FloatField = null;
+            Assert.IsNull(fields[TestWellKnownTypes.StringFieldFieldNumber].Accessor.GetValue(message));
+            Assert.IsNull(fields[TestWellKnownTypes.FloatFieldFieldNumber].Accessor.GetValue(message));
+        }
+
+        [Test]
+        public void Reflection_RepeatedFields()
+        {
+            // Just a single example... note that we can't have a null value here
+            var message = new RepeatedWellKnownTypes { Int32Field = { 1, 2 } };
+            var fields = RepeatedWellKnownTypes.Descriptor.Fields;
+            var list = (IList) fields[RepeatedWellKnownTypes.Int32FieldFieldNumber].Accessor.GetValue(message);
+            CollectionAssert.AreEqual(new[] { 1, 2 }, list);
+        }
+
+        [Test]
+        public void Reflection_MapFields()
+        {
+            // Just a single example... note that we can't have a null value here despite the value type being int?
+            var message = new MapWellKnownTypes { Int32Field = { { 1, 2 } } };
+            var fields = MapWellKnownTypes.Descriptor.Fields;
+            var dictionary = (IDictionary) fields[MapWellKnownTypes.Int32FieldFieldNumber].Accessor.GetValue(message);
+            Assert.AreEqual(2, dictionary[1]);
+        }
+
+        [Test]
+        public void Oneof()
+        {
+            var message = new OneofWellKnownTypes { EmptyField = new Empty() };
+            // Start off with a non-wrapper
+            Assert.AreEqual(OneofWellKnownTypes.OneofFieldOneofCase.EmptyField, message.OneofFieldCase);
+            AssertOneofRoundTrip(message);
+
+            message.StringField = "foo";
+            Assert.AreEqual(OneofWellKnownTypes.OneofFieldOneofCase.StringField, message.OneofFieldCase);
+            AssertOneofRoundTrip(message);
+
+            message.StringField = "foo";
+            Assert.AreEqual(OneofWellKnownTypes.OneofFieldOneofCase.StringField, message.OneofFieldCase);
+            AssertOneofRoundTrip(message);
+
+            message.DoubleField = 0.0f;
+            Assert.AreEqual(OneofWellKnownTypes.OneofFieldOneofCase.DoubleField, message.OneofFieldCase);
+            AssertOneofRoundTrip(message);
+
+            message.DoubleField = 1.0f;
+            Assert.AreEqual(OneofWellKnownTypes.OneofFieldOneofCase.DoubleField, message.OneofFieldCase);
+            AssertOneofRoundTrip(message);
+
+            message.ClearOneofField();
+            Assert.AreEqual(OneofWellKnownTypes.OneofFieldOneofCase.None, message.OneofFieldCase);
+            AssertOneofRoundTrip(message);
+        }
+
+        private void AssertOneofRoundTrip(OneofWellKnownTypes message)
+        {
+            // Normal roundtrip, but explicitly checking the case...
+            var bytes = message.ToByteArray();
+            var parsed = OneofWellKnownTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+            Assert.AreEqual(message.OneofFieldCase, parsed.OneofFieldCase);
+        }
+
+        [Test]
+        [TestCase("x", "y", "y")]
+        [TestCase("x", "", "x")]
+        [TestCase("x", null, "x")]
+        [TestCase("", "y", "y")]
+        [TestCase("", "", "")]
+        [TestCase("", null, "")]
+        [TestCase(null, "y", "y")]
+        [TestCase(null, "", "")]
+        [TestCase(null, null, null)]
+        public void Merging(string original, string merged, string expected)
+        {
+            var originalMessage = new TestWellKnownTypes { StringField = original };
+            var mergingMessage = new TestWellKnownTypes { StringField = merged };
+            originalMessage.MergeFrom(mergingMessage);
+            Assert.AreEqual(expected, originalMessage.StringField);
+
+            // Try it using MergeFrom(CodedInputStream) too...
+            originalMessage = new TestWellKnownTypes { StringField = original };
+            originalMessage.MergeFrom(mergingMessage.ToByteArray());
+            Assert.AreEqual(expected, originalMessage.StringField);
+        }
+
+        // Merging is odd with wrapper types, due to the way that default values aren't emitted in
+        // the binary stream. In fact we cheat a little bit - a message with an explicitly present default
+        // value will have that default value ignored. See issue 615. Fixing this would require significant upheaval to
+        // the FieldCodec side of things.
+        [Test]
+        public void MergingStreamExplicitValue()
+        {
+            var message = new TestWellKnownTypes { Int32Field = 5 };
+
+            // Create a byte array which has the data of an Int32Value explicitly containing a value of 0.
+            // This wouldn't normally happen.
+            byte[] bytes;
+            var wrapperTag = WireFormat.MakeTag(TestWellKnownTypes.Int32FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            var valueTag = WireFormat.MakeTag(Int32Value.ValueFieldNumber, WireFormat.WireType.Varint);
+            using (var stream = new MemoryStream())
+            {
+                var coded = new CodedOutputStream(stream);
+                coded.WriteTag(wrapperTag);
+                coded.WriteLength(2); // valueTag + a value 0, each one byte
+                coded.WriteTag(valueTag);
+                coded.WriteInt32(0);
+                coded.Flush();
+                bytes = stream.ToArray();
+            }
+
+            message.MergeFrom(bytes);
+            // A normal implementation would have 0 now, as the explicit default would have been overwritten the 5.
+            // With the FieldCodec for Nullable<int>, we can't tell the difference between an implicit 0 and an explicit 0.
+            Assert.AreEqual(5, message.Int32Field);
+        }
+
+        [Test]
+        public void MergingStreamNoValue()
+        {
+            var message = new TestWellKnownTypes { Int32Field = 5 };
+
+            // Create a byte array which an Int32 field, but with no value.
+            var bytes = new TestWellKnownTypes { Int32Field = 0 }.ToByteArray();
+            Assert.AreEqual(2, bytes.Length); // The tag for Int32Field is a single byte, then a byte indicating a 0-length message.
+            message.MergeFrom(bytes);
+
+            // The "implicit" 0 did *not* overwrite the value.
+            // (This is the correct behaviour.)
+            Assert.AreEqual(5, message.Int32Field);
+        }
+
+        // All permutations of origin/merging value being null, zero (default) or non-default.
+        // As this is the in-memory version, we don't need to worry about the difference between implicit and explicit 0.
+        [Test]
+        [TestCase(null, null, null)]
+        [TestCase(null, 0, 0)]
+        [TestCase(null, 5, 5)]
+        [TestCase(0, null, 0)]
+        [TestCase(0, 0, 0)]
+        [TestCase(0, 5, 5)]
+        [TestCase(5, null, 5)]
+        [TestCase(5, 0, 5)]
+        [TestCase(5, 10, 10)]
+        public void MergingMessageWithZero(int? originValue, int? mergingValue, int? expectedResult)
+        {
+            // This differs from the MergingStreamCornerCase because when we merge message *objects*,
+            // we ignore default values from the "source".
+            var message1 = new TestWellKnownTypes { Int32Field = originValue };
+            var message2 = new TestWellKnownTypes { Int32Field = mergingValue };
+            message1.MergeFrom(message2);
+            Assert.AreEqual(expectedResult, message1.Int32Field);
+        }
+
+        [Test]
+        public void UnknownFieldInWrapper()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            var wrapperTag = WireFormat.MakeTag(TestWellKnownTypes.Int32FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            var unknownTag = WireFormat.MakeTag(15, WireFormat.WireType.Varint);
+            var valueTag = WireFormat.MakeTag(Int32Value.ValueFieldNumber, WireFormat.WireType.Varint);
+
+            output.WriteTag(wrapperTag);
+            output.WriteLength(4); // unknownTag + value 5 + valueType + value 6, each 1 byte
+            output.WriteTag(unknownTag);
+            output.WriteInt32((int) valueTag); // Sneakily "pretend" it's a tag when it's really a value
+            output.WriteTag(valueTag);
+            output.WriteInt32(6);
+
+            output.Flush();
+            stream.Position = 0;
+            
+            var message = TestWellKnownTypes.Parser.ParseFrom(stream);
+            Assert.AreEqual(6, message.Int32Field);
+        }
+
+        [Test]
+        public void ClearWithReflection()
+        {
+            // String and Bytes are the tricky ones here, as the CLR type of the property
+            // is the same between the wrapper and non-wrapper types.
+            var message = new TestWellKnownTypes { StringField = "foo" };
+            TestWellKnownTypes.Descriptor.Fields[TestWellKnownTypes.StringFieldFieldNumber].Accessor.Clear(message);
+            Assert.IsNull(message.StringField);
+        }
+    }
+}
diff --git a/csharp/compatibility_tests/v3.0.0/test.sh b/csharp/compatibility_tests/v3.0.0/test.sh
new file mode 100755
index 0000000..54d28df
--- /dev/null
+++ b/csharp/compatibility_tests/v3.0.0/test.sh
@@ -0,0 +1,104 @@
+#!/bin/bash
+
+function run_test() {
+  # Generate test proto files.
+  ./protoc_1 -Iprotos/src -I../../../src/ --csharp_out=src/Google.Protobuf.Test \
+    --csharp_opt=base_namespace=Google.Protobuf \
+    protos/src/google/protobuf/unittest_import_proto3.proto \
+    protos/src/google/protobuf/unittest_import_public_proto3.proto \
+    protos/src/google/protobuf/unittest_well_known_types.proto
+
+  ./protoc_1 -Iprotos/csharp --csharp_out=src/Google.Protobuf.Test \
+    --csharp_opt=base_namespace=UnitTest.Issues \
+    protos/csharp/protos/unittest_issues.proto
+
+  ./protoc_2 -Iprotos/src --csharp_out=src/Google.Protobuf.Test \
+    --csharp_opt=base_namespace=Google.Protobuf \
+    protos/src/google/protobuf/unittest_proto3.proto \
+    protos/src/google/protobuf/map_unittest_proto3.proto
+
+  # Build and test.
+  dotnet restore src/Google.Protobuf/Google.Protobuf.csproj
+  dotnet restore src/Google.Protobuf.Test/Google.Protobuf.Test.csproj
+  dotnet build -c Release src/Google.Protobuf/Google.Protobuf.csproj
+  dotnet build -c Release src/Google.Protobuf.Test/Google.Protobuf.Test.csproj
+  dotnet run -c Release -f netcoreapp1.0 -p src/Google.Protobuf.Test/Google.Protobuf.Test.csproj
+}
+
+set -ex
+
+# Change to the script's directory.
+cd $(dirname $0)
+
+# Version of the tests (i.e., the version of protobuf from where we extracted
+# these tests).
+TEST_VERSION=3.0.0
+
+# The old version of protobuf that we are testing compatibility against. This
+# is usually the same as TEST_VERSION (i.e., we use the tests extracted from
+# that version to test compatibility of the newest runtime against it), but it
+# is also possible to use this same test set to test the compatibiilty of the
+# latest version against other versions.
+case "$1" in
+  ""|3.0.0)
+    OLD_VERSION=3.0.0
+    OLD_VERSION_PROTOC=http://repo1.maven.org/maven2/com/google/protobuf/protoc/3.0.0/protoc-3.0.0-linux-x86_64.exe
+    ;;
+  3.0.2)
+    OLD_VERSION=3.0.2
+    OLD_VERSION_PROTOC=http://repo1.maven.org/maven2/com/google/protobuf/protoc/3.0.2/protoc-3.0.2-linux-x86_64.exe
+    ;;
+  3.1.0)
+    OLD_VERSION=3.1.0
+    OLD_VERSION_PROTOC=http://repo1.maven.org/maven2/com/google/protobuf/protoc/3.1.0/protoc-3.1.0-linux-x86_64.exe
+    ;;
+  *)
+    echo "[ERROR]: Unknown version number: $1"
+    exit 1
+    ;;
+esac
+
+echo "Running compatibility tests with $OLD_VERSION"
+
+# Check protoc
+[ -f ../../../src/protoc ] || {
+  echo "[ERROR]: Please build protoc first."
+  exit 1
+}
+
+# Download old version protoc compiler (for linux).
+wget $OLD_VERSION_PROTOC -O old_protoc
+chmod +x old_protoc
+
+# Test source compatibility. In these tests we recompile everything against
+# the new runtime (including old version generated code).
+# Copy the new runtime and keys.
+cp ../../src/Google.Protobuf src/Google.Protobuf -r
+cp ../../keys . -r
+
+# Test A.1:
+#   proto set 1: use old version
+#   proto set 2 which may import protos in set 1: use old version
+cp old_protoc protoc_1
+cp old_protoc protoc_2
+run_test
+
+# Test A.2:
+#   proto set 1: use new version
+#   proto set 2 which may import protos in set 1: use old version
+cp ../../../src/protoc protoc_1
+cp old_protoc protoc_2
+run_test
+
+# Test A.3:
+#   proto set 1: use old version
+#   proto set 2 which may import protos in set 1: use new version
+cp old_protoc protoc_1
+cp ../../../src/protoc protoc_2
+run_test
+
+rm protoc_1
+rm protoc_2
+rm old_protoc
+rm keys -r
+rm src/Google.Protobuf -r