diff --git a/objectivec/Tests/GPBDescriptorTests.m b/objectivec/Tests/GPBDescriptorTests.m
new file mode 100644
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+++ b/objectivec/Tests/GPBDescriptorTests.m
@@ -0,0 +1,232 @@
+// 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 <objc/runtime.h>
+
+#import "GPBDescriptor.h"
+#import "google/protobuf/Unittest.pbobjc.h"
+
+@interface DescriptorTests : GPBTestCase
+@end
+
+@implementation DescriptorTests
+
+- (void)testFieldDescriptor {
+  GPBDescriptor *descriptor = [TestAllTypes descriptor];
+
+  // Nested Enum
+  GPBFieldDescriptor *fieldDescriptorWithName =
+      [descriptor fieldWithName:@"optionalNestedEnum"];
+  XCTAssertNotNil(fieldDescriptorWithName);
+  GPBFieldDescriptor *fieldDescriptorWithNumber =
+      [descriptor fieldWithNumber:21];
+  XCTAssertNotNil(fieldDescriptorWithNumber);
+  XCTAssertEqual(fieldDescriptorWithName, fieldDescriptorWithNumber);
+  XCTAssertNotNil(fieldDescriptorWithNumber.enumDescriptor);
+  XCTAssertEqualObjects(fieldDescriptorWithNumber.enumDescriptor.name,
+                        @"TestAllTypes_NestedEnum");
+
+  // Foreign Enum
+  fieldDescriptorWithName = [descriptor fieldWithName:@"optionalForeignEnum"];
+  XCTAssertNotNil(fieldDescriptorWithName);
+  fieldDescriptorWithNumber = [descriptor fieldWithNumber:22];
+  XCTAssertNotNil(fieldDescriptorWithNumber);
+  XCTAssertEqual(fieldDescriptorWithName, fieldDescriptorWithNumber);
+  XCTAssertNotNil(fieldDescriptorWithNumber.enumDescriptor);
+  XCTAssertEqualObjects(fieldDescriptorWithNumber.enumDescriptor.name,
+                        @"ForeignEnum");
+
+  // Import Enum
+  fieldDescriptorWithName = [descriptor fieldWithName:@"optionalImportEnum"];
+  XCTAssertNotNil(fieldDescriptorWithName);
+  fieldDescriptorWithNumber = [descriptor fieldWithNumber:23];
+  XCTAssertNotNil(fieldDescriptorWithNumber);
+  XCTAssertEqual(fieldDescriptorWithName, fieldDescriptorWithNumber);
+  XCTAssertNotNil(fieldDescriptorWithNumber.enumDescriptor);
+  XCTAssertEqualObjects(fieldDescriptorWithNumber.enumDescriptor.name,
+                        @"ImportEnum");
+
+  // Nested Message
+  fieldDescriptorWithName = [descriptor fieldWithName:@"optionalNestedMessage"];
+  XCTAssertNotNil(fieldDescriptorWithName);
+  fieldDescriptorWithNumber = [descriptor fieldWithNumber:18];
+  XCTAssertNotNil(fieldDescriptorWithNumber);
+  XCTAssertEqual(fieldDescriptorWithName, fieldDescriptorWithNumber);
+  XCTAssertNil(fieldDescriptorWithNumber.enumDescriptor);
+
+  // Foreign Message
+  fieldDescriptorWithName =
+      [descriptor fieldWithName:@"optionalForeignMessage"];
+  XCTAssertNotNil(fieldDescriptorWithName);
+  fieldDescriptorWithNumber = [descriptor fieldWithNumber:19];
+  XCTAssertNotNil(fieldDescriptorWithNumber);
+  XCTAssertEqual(fieldDescriptorWithName, fieldDescriptorWithNumber);
+  XCTAssertNil(fieldDescriptorWithNumber.enumDescriptor);
+
+  // Import Message
+  fieldDescriptorWithName = [descriptor fieldWithName:@"optionalImportMessage"];
+  XCTAssertNotNil(fieldDescriptorWithName);
+  fieldDescriptorWithNumber = [descriptor fieldWithNumber:20];
+  XCTAssertNotNil(fieldDescriptorWithNumber);
+  XCTAssertEqual(fieldDescriptorWithName, fieldDescriptorWithNumber);
+  XCTAssertNil(fieldDescriptorWithNumber.enumDescriptor);
+}
+
+- (void)testEnumDescriptor {
+  GPBEnumDescriptor *descriptor = TestAllTypes_NestedEnum_EnumDescriptor();
+
+  NSString *enumName = [descriptor enumNameForValue:1];
+  XCTAssertNotNil(enumName);
+  int32_t value;
+  XCTAssertTrue(
+      [descriptor getValue:&value forEnumName:@"TestAllTypes_NestedEnum_Foo"]);
+  XCTAssertTrue(
+      [descriptor getValue:NULL forEnumName:@"TestAllTypes_NestedEnum_Foo"]);
+  XCTAssertEqual(value, TestAllTypes_NestedEnum_Foo);
+
+  enumName = [descriptor enumNameForValue:2];
+  XCTAssertNotNil(enumName);
+  XCTAssertTrue(
+      [descriptor getValue:&value forEnumName:@"TestAllTypes_NestedEnum_Bar"]);
+  XCTAssertEqual(value, TestAllTypes_NestedEnum_Bar);
+
+  enumName = [descriptor enumNameForValue:3];
+  XCTAssertNotNil(enumName);
+  XCTAssertTrue(
+      [descriptor getValue:&value forEnumName:@"TestAllTypes_NestedEnum_Baz"]);
+  XCTAssertEqual(value, TestAllTypes_NestedEnum_Baz);
+
+  // Bad values
+  enumName = [descriptor enumNameForValue:0];
+  XCTAssertNil(enumName);
+  XCTAssertFalse([descriptor getValue:&value forEnumName:@"Unknown"]);
+  XCTAssertFalse([descriptor getValue:NULL forEnumName:@"Unknown"]);
+  XCTAssertFalse([descriptor getValue:&value
+                          forEnumName:@"TestAllTypes_NestedEnum_Unknown"]);
+  XCTAssertFalse([descriptor getValue:NULL
+                          forEnumName:@"TestAllTypes_NestedEnum_Unknown"]);
+}
+
+- (void)testEnumValueValidator {
+  GPBDescriptor *descriptor = [TestAllTypes descriptor];
+  GPBFieldDescriptor *fieldDescriptor =
+      [descriptor fieldWithName:@"optionalNestedEnum"];
+
+  // Valid values
+  XCTAssertTrue([fieldDescriptor isValidEnumValue:1]);
+  XCTAssertTrue([fieldDescriptor isValidEnumValue:2]);
+  XCTAssertTrue([fieldDescriptor isValidEnumValue:3]);
+  XCTAssertTrue([fieldDescriptor isValidEnumValue:-1]);
+
+  // Invalid values
+  XCTAssertFalse([fieldDescriptor isValidEnumValue:4]);
+  XCTAssertFalse([fieldDescriptor isValidEnumValue:0]);
+  XCTAssertFalse([fieldDescriptor isValidEnumValue:-2]);
+}
+
+- (void)testEnumDescriptorLookup {
+  GPBDescriptor *descriptor = [TestAllTypes descriptor];
+  GPBEnumDescriptor *enumDescriptor =
+      [descriptor enumWithName:@"TestAllTypes_NestedEnum"];
+  XCTAssertNotNil(enumDescriptor);
+
+  // Descriptor cannot find foreign or imported enums.
+  enumDescriptor = [descriptor enumWithName:@"ForeignEnumEnum"];
+  XCTAssertNil(enumDescriptor);
+  enumDescriptor = [descriptor enumWithName:@"ImportEnumEnum"];
+  XCTAssertNil(enumDescriptor);
+}
+
+- (void)testOneofDescriptor {
+  GPBDescriptor *descriptor = [TestOneof2 descriptor];
+
+  // All fields should be listed.
+  XCTAssertEqual(descriptor.fields.count, 17U);
+
+  // There are two oneofs in there.
+  XCTAssertEqual(descriptor.oneofs.count, 2U);
+
+  GPBFieldDescriptor *fooStringField =
+      [descriptor fieldWithNumber:TestOneof2_FieldNumber_FooString];
+  XCTAssertNotNil(fooStringField);
+  GPBFieldDescriptor *barStringField =
+      [descriptor fieldWithNumber:TestOneof2_FieldNumber_BarString];
+  XCTAssertNotNil(barStringField);
+
+  // Check the oneofs to have what is expected.
+
+  GPBOneofDescriptor *oneofFoo = [descriptor oneofWithName:@"foo"];
+  XCTAssertNotNil(oneofFoo);
+  XCTAssertEqual(oneofFoo.fields.count, 9U);
+
+  // Pointer comparisons.
+  XCTAssertEqual([oneofFoo fieldWithNumber:TestOneof2_FieldNumber_FooString],
+                 fooStringField);
+  XCTAssertEqual([oneofFoo fieldWithName:@"fooString"], fooStringField);
+
+  GPBOneofDescriptor *oneofBar = [descriptor oneofWithName:@"bar"];
+  XCTAssertNotNil(oneofBar);
+  XCTAssertEqual(oneofBar.fields.count, 6U);
+
+  // Pointer comparisons.
+  XCTAssertEqual([oneofBar fieldWithNumber:TestOneof2_FieldNumber_BarString],
+                 barStringField);
+  XCTAssertEqual([oneofBar fieldWithName:@"barString"], barStringField);
+
+  // Unknown oneof not found.
+
+  XCTAssertNil([descriptor oneofWithName:@"mumble"]);
+  XCTAssertNil([descriptor oneofWithName:@"Foo"]);
+
+  // Unknown oneof item.
+
+  XCTAssertNil([oneofFoo fieldWithName:@"mumble"]);
+  XCTAssertNil([oneofFoo fieldWithNumber:666]);
+
+  // Field exists, but not in this oneof.
+
+  XCTAssertNil([oneofFoo fieldWithName:@"barString"]);
+  XCTAssertNil([oneofFoo fieldWithNumber:TestOneof2_FieldNumber_BarString]);
+  XCTAssertNil([oneofBar fieldWithName:@"fooString"]);
+  XCTAssertNil([oneofBar fieldWithNumber:TestOneof2_FieldNumber_FooString]);
+
+  // Check pointers back to the enclosing oneofs.
+  // (pointer comparisions)
+  XCTAssertEqual(fooStringField.containingOneof, oneofFoo);
+  XCTAssertEqual(barStringField.containingOneof, oneofBar);
+  GPBFieldDescriptor *bazString =
+      [descriptor fieldWithNumber:TestOneof2_FieldNumber_BazString];
+  XCTAssertNotNil(bazString);
+  XCTAssertNil(bazString.containingOneof);
+}
+
+@end