diff --git a/objectivec/Tests/GPBWireFormatTests.m b/objectivec/Tests/GPBWireFormatTests.m
new file mode 100644
index 0000000..2a406f1
--- /dev/null
+++ b/objectivec/Tests/GPBWireFormatTests.m
@@ -0,0 +1,252 @@
+// 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.
+
+#import "GPBTestUtilities.h"
+
+#import "GPBCodedInputStream.h"
+#import "GPBMessage_PackagePrivate.h"
+#import "GPBUnknownField_PackagePrivate.h"
+#import "google/protobuf/Unittest.pbobjc.h"
+#import "google/protobuf/UnittestMset.pbobjc.h"
+#import "google/protobuf/UnittestMsetWireFormat.pbobjc.h"
+
+@interface WireFormatTests : GPBTestCase
+@end
+
+@implementation WireFormatTests
+
+- (void)testSerialization {
+  TestAllTypes* message = [self allSetRepeatedCount:kGPBDefaultRepeatCount];
+
+  NSData* rawBytes = message.data;
+  XCTAssertEqual(message.serializedSize, (size_t)rawBytes.length);
+
+  TestAllTypes* message2 = [TestAllTypes parseFromData:rawBytes error:NULL];
+
+  [self assertAllFieldsSet:message2 repeatedCount:kGPBDefaultRepeatCount];
+}
+
+- (void)testSerializationPacked {
+  TestPackedTypes* message =
+      [self packedSetRepeatedCount:kGPBDefaultRepeatCount];
+
+  NSData* rawBytes = message.data;
+  XCTAssertEqual(message.serializedSize, (size_t)rawBytes.length);
+
+  TestPackedTypes* message2 =
+      [TestPackedTypes parseFromData:rawBytes error:NULL];
+
+  [self assertPackedFieldsSet:message2 repeatedCount:kGPBDefaultRepeatCount];
+}
+
+- (void)testSerializeExtensions {
+  // TestAllTypes and TestAllExtensions should have compatible wire formats,
+  // so if we serealize a TestAllExtensions then parse it as TestAllTypes
+  // it should work.
+
+  TestAllExtensions* message =
+      [self allExtensionsSetRepeatedCount:kGPBDefaultRepeatCount];
+  NSData* rawBytes = message.data;
+  XCTAssertEqual(message.serializedSize, (size_t)rawBytes.length);
+
+  TestAllTypes* message2 = [TestAllTypes parseFromData:rawBytes error:NULL];
+
+  [self assertAllFieldsSet:message2 repeatedCount:kGPBDefaultRepeatCount];
+}
+
+- (void)testSerializePackedExtensions {
+  // TestPackedTypes and TestPackedExtensions should have compatible wire
+  // formats; check that they serialize to the same string.
+  TestPackedExtensions* message =
+      [self packedExtensionsSetRepeatedCount:kGPBDefaultRepeatCount];
+  NSData* rawBytes = message.data;
+
+  TestPackedTypes* message2 =
+      [self packedSetRepeatedCount:kGPBDefaultRepeatCount];
+  NSData* rawBytes2 = message2.data;
+
+  XCTAssertEqualObjects(rawBytes, rawBytes2);
+}
+
+- (void)testParseExtensions {
+  // TestAllTypes and TestAllExtensions should have compatible wire formats,
+  // so if we serialize a TestAllTypes then parse it as TestAllExtensions
+  // it should work.
+
+  TestAllTypes* message = [self allSetRepeatedCount:kGPBDefaultRepeatCount];
+  NSData* rawBytes = message.data;
+
+  GPBExtensionRegistry* registry = [self extensionRegistry];
+
+  TestAllExtensions* message2 = [TestAllExtensions parseFromData:rawBytes
+                                               extensionRegistry:registry
+                                                           error:NULL];
+
+  [self assertAllExtensionsSet:message2 repeatedCount:kGPBDefaultRepeatCount];
+}
+
+
+- (void) testExtensionsSerializedSize {
+  size_t allSet = [self allSetRepeatedCount:kGPBDefaultRepeatCount].serializedSize;
+  size_t extensionSet = [self allExtensionsSetRepeatedCount:kGPBDefaultRepeatCount].serializedSize;
+  XCTAssertEqual(allSet, extensionSet);
+}
+
+- (void)testParsePackedExtensions {
+  // Ensure that packed extensions can be properly parsed.
+  TestPackedExtensions* message =
+      [self packedExtensionsSetRepeatedCount:kGPBDefaultRepeatCount];
+  NSData* rawBytes = message.data;
+
+  GPBExtensionRegistry* registry = [self extensionRegistry];
+
+  TestPackedExtensions* message2 = [TestPackedExtensions parseFromData:rawBytes
+                                                     extensionRegistry:registry
+                                                                 error:NULL];
+
+  [self assertPackedExtensionsSet:message2
+                    repeatedCount:kGPBDefaultRepeatCount];
+}
+
+const int kUnknownTypeId = 1550055;
+
+- (void)testSerializeMessageSet {
+  // Set up a TestMessageSet with two known messages and an unknown one.
+  TestMessageSet* message_set = [TestMessageSet message];
+  [[message_set getExtension:[TestMessageSetExtension1 messageSetExtension]]
+      setI:123];
+  [[message_set getExtension:[TestMessageSetExtension2 messageSetExtension]]
+      setStr:@"foo"];
+  GPBUnknownField* unknownField =
+      [[[GPBUnknownField alloc] initWithNumber:kUnknownTypeId] autorelease];
+  [unknownField addLengthDelimited:[NSData dataWithBytes:"bar" length:3]];
+  GPBUnknownFieldSet* unknownFieldSet =
+      [[[GPBUnknownFieldSet alloc] init] autorelease];
+  [unknownFieldSet addField:unknownField];
+  [message_set setUnknownFields:unknownFieldSet];
+
+  NSData* data = [message_set data];
+
+  // Parse back using RawMessageSet and check the contents.
+  RawMessageSet* raw = [RawMessageSet parseFromData:data error:NULL];
+
+  XCTAssertEqual([raw.unknownFields countOfFields], (NSUInteger)0);
+
+  XCTAssertEqual(raw.itemArray.count, (NSUInteger)3);
+  XCTAssertEqual((uint32_t)[raw.itemArray[0] typeId],
+                 [TestMessageSetExtension1 messageSetExtension].fieldNumber);
+  XCTAssertEqual((uint32_t)[raw.itemArray[1] typeId],
+                 [TestMessageSetExtension2 messageSetExtension].fieldNumber);
+  XCTAssertEqual([raw.itemArray[2] typeId], kUnknownTypeId);
+
+  TestMessageSetExtension1* message1 =
+      [TestMessageSetExtension1 parseFromData:[((RawMessageSet_Item*)raw.itemArray[0]) message]
+                                        error:NULL];
+  XCTAssertEqual(message1.i, 123);
+
+  TestMessageSetExtension2* message2 =
+      [TestMessageSetExtension2 parseFromData:[((RawMessageSet_Item*)raw.itemArray[1]) message]
+                                        error:NULL];
+  XCTAssertEqualObjects(message2.str, @"foo");
+
+  XCTAssertEqualObjects([raw.itemArray[2] message],
+                        [NSData dataWithBytes:"bar" length:3]);
+}
+
+- (void)testParseMessageSet {
+  // Set up a RawMessageSet with two known messages and an unknown one.
+  RawMessageSet* raw = [RawMessageSet message];
+
+  {
+    RawMessageSet_Item* item = [RawMessageSet_Item message];
+    item.typeId = [TestMessageSetExtension1 messageSetExtension].fieldNumber;
+    TestMessageSetExtension1* message = [TestMessageSetExtension1 message];
+    message.i = 123;
+    item.message = [message data];
+    [raw.itemArray addObject:item];
+  }
+
+  {
+    RawMessageSet_Item* item = [RawMessageSet_Item message];
+    item.typeId = [TestMessageSetExtension2 messageSetExtension].fieldNumber;
+    TestMessageSetExtension2* message = [TestMessageSetExtension2 message];
+    message.str = @"foo";
+    item.message = [message data];
+    [raw.itemArray addObject:item];
+  }
+
+  {
+    RawMessageSet_Item* item = [RawMessageSet_Item message];
+    item.typeId = kUnknownTypeId;
+    item.message = [NSData dataWithBytes:"bar" length:3];
+    [raw.itemArray addObject:item];
+  }
+
+  NSData* data = [raw data];
+
+  // Parse as a TestMessageSet and check the contents.
+  TestMessageSet* messageSet =
+      [TestMessageSet parseFromData:data
+                  extensionRegistry:[UnittestMsetRoot extensionRegistry]
+                              error:NULL];
+
+  XCTAssertEqual(
+      [[messageSet
+          getExtension:[TestMessageSetExtension1 messageSetExtension]] i],
+      123);
+  XCTAssertEqualObjects(
+      [[messageSet
+          getExtension:[TestMessageSetExtension2 messageSetExtension]] str],
+      @"foo");
+
+  XCTAssertEqual([messageSet.unknownFields countOfFields], (NSUInteger)1);
+  GPBUnknownField* unknownField = [messageSet.unknownFields getField:kUnknownTypeId];
+  XCTAssertNotNil(unknownField);
+  XCTAssertEqual(unknownField.lengthDelimitedList.count, (NSUInteger)1);
+  XCTAssertEqualObjects(unknownField.lengthDelimitedList[0],
+                        [NSData dataWithBytes:"bar" length:3]);
+}
+
+- (void)assertFieldsInOrder:(NSData*)data {
+  GPBCodedInputStream* input = [GPBCodedInputStream streamWithData:data];
+  int32_t previousTag = 0;
+
+  while (YES) {
+    int32_t tag = [input readTag];
+    if (tag == 0) {
+      break;
+    }
+
+    XCTAssertGreaterThan(tag, previousTag);
+    [input skipField:tag];
+  }
+}
+
+@end