diff --git a/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.cs b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.cs
new file mode 100644
index 0000000..14cc6d1
--- /dev/null
+++ b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.cs
@@ -0,0 +1,715 @@
+﻿#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.FOREIGN_UNSPECIFIED, message.SingleForeignEnum);
+            Assert.IsNull(message.SingleForeignMessage);
+            Assert.AreEqual(ImportEnum.IMPORT_ENUM_UNSPECIFIED, message.SingleImportEnum);
+            Assert.IsNull(message.SingleImportMessage);
+            Assert.AreEqual(0, message.SingleInt32);
+            Assert.AreEqual(0L, message.SingleInt64);
+            Assert.AreEqual(TestAllTypes.Types.NestedEnum.NESTED_ENUM_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.FOREIGN_BAR,
+                SingleForeignMessage = new ForeignMessage { C = 10 },
+                SingleImportEnum = ImportEnum.IMPORT_BAZ,
+                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.FOREIGN_FOO, ForeignEnum.FOREIGN_BAR },
+                RepeatedForeignMessage = { new ForeignMessage(), new ForeignMessage { C = 10 } },
+                RepeatedImportEnum = { ImportEnum.IMPORT_BAZ, ImportEnum.IMPORT_ENUM_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.MAP_ENUM_BAR },
+                    { 2000, MapEnum.MAP_ENUM_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 IgnoreUnknownFields_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);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void IgnoreUnknownFields_AllTypes()
+        {
+            // Simple way of ensuring we can skip all kinds of fields.
+            var data = SampleMessages.CreateFullTestAllTypes().ToByteArray();
+            var empty = Empty.Parser.ParseFrom(data);
+            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 ExtraEndGroupSkipped()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+
+            output.WriteTag(100, WireFormat.WireType.EndGroup);
+            output.WriteTag(TestAllTypes.SingleFixed32FieldNumber, WireFormat.WireType.Fixed32);
+            output.WriteFixed32(123);
+
+            output.Flush();
+
+            stream.Position = 0;
+            var parsed = TestAllTypes.Parser.ParseFrom(stream);
+            Assert.AreEqual(new TestAllTypes { SingleFixed32 = 123 }, parsed);
+        }
+
+        [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));
+        }
+    }
+}