diff --git a/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
new file mode 100644
index 0000000..b613cc8
--- /dev/null
+++ b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
@@ -0,0 +1,268 @@
+﻿using Google.Protobuf.TestProtos.Proto2;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    /// <summary>
+    /// Tests around the generated TestAllTypes message in unittest.proto
+    /// </summary>
+    public partial class GeneratedMessageTest
+    {
+        [Test]
+        public void DefaultProto2Values()
+        {
+            var message = new TestAllTypes();
+            Assert.AreEqual(false, message.OptionalBool);
+            Assert.AreEqual(ByteString.Empty, message.OptionalBytes);
+            Assert.AreEqual(0.0, message.OptionalDouble);
+            Assert.AreEqual(0, message.OptionalFixed32);
+            Assert.AreEqual(0L, message.OptionalFixed64);
+            Assert.AreEqual(0.0f, message.OptionalFloat);
+            Assert.AreEqual(ForeignEnum.ForeignFoo, message.OptionalForeignEnum);
+            Assert.IsNull(message.OptionalForeignMessage);
+            Assert.AreEqual(ImportEnum.ImportFoo, message.OptionalImportEnum);
+            Assert.IsNull(message.OptionalImportMessage);
+            Assert.AreEqual(0, message.OptionalInt32);
+            Assert.AreEqual(0L, message.OptionalInt64);
+            Assert.AreEqual(TestAllTypes.Types.NestedEnum.Foo, message.OptionalNestedEnum);
+            Assert.IsNull(message.OptionalNestedMessage);
+            Assert.IsNull(message.OptionalPublicImportMessage);
+            Assert.AreEqual(0, message.OptionalSfixed32);
+            Assert.AreEqual(0L, message.OptionalSfixed64);
+            Assert.AreEqual(0, message.OptionalSint32);
+            Assert.AreEqual(0L, message.OptionalSint64);
+            Assert.AreEqual("", message.OptionalString);
+            Assert.AreEqual(0U, message.OptionalUint32);
+            Assert.AreEqual(0UL, message.OptionalUint64);
+
+            // 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.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);
+
+            Assert.AreEqual(true, message.DefaultBool);
+            Assert.AreEqual(ByteString.CopyFromUtf8("world"), message.DefaultBytes);
+            Assert.AreEqual("123", message.DefaultCord);
+            Assert.AreEqual(52e3, message.DefaultDouble);
+            Assert.AreEqual(47, message.DefaultFixed32);
+            Assert.AreEqual(48, message.DefaultFixed64);
+            Assert.AreEqual(51.5, message.DefaultFloat);
+            Assert.AreEqual(ForeignEnum.ForeignBar, message.DefaultForeignEnum);
+            Assert.AreEqual(ImportEnum.ImportBar, message.DefaultImportEnum);
+            Assert.AreEqual(41, message.DefaultInt32);
+            Assert.AreEqual(42, message.DefaultInt64);
+            Assert.AreEqual(TestAllTypes.Types.NestedEnum.Bar, message.DefaultNestedEnum);
+            Assert.AreEqual(49, message.DefaultSfixed32);
+            Assert.AreEqual(-50, message.DefaultSfixed64);
+            Assert.AreEqual(-45, message.DefaultSint32);
+            Assert.AreEqual(46, message.DefaultSint64);
+            Assert.AreEqual("hello", message.DefaultString);
+            Assert.AreEqual("abc", message.DefaultStringPiece);
+            Assert.AreEqual(43, message.DefaultUint32);
+            Assert.AreEqual(44, message.DefaultUint64);
+
+            Assert.False(message.HasDefaultBool);
+            Assert.False(message.HasDefaultBytes);
+            Assert.False(message.HasDefaultCord);
+            Assert.False(message.HasDefaultDouble);
+            Assert.False(message.HasDefaultFixed32);
+            Assert.False(message.HasDefaultFixed64);
+            Assert.False(message.HasDefaultFloat);
+            Assert.False(message.HasDefaultForeignEnum);
+            Assert.False(message.HasDefaultImportEnum);
+            Assert.False(message.HasDefaultInt32);
+            Assert.False(message.HasDefaultInt64);
+            Assert.False(message.HasDefaultNestedEnum);
+            Assert.False(message.HasDefaultSfixed32);
+            Assert.False(message.HasDefaultSfixed64);
+            Assert.False(message.HasDefaultSint32);
+            Assert.False(message.HasDefaultSint64);
+            Assert.False(message.HasDefaultString);
+            Assert.False(message.HasDefaultStringPiece);
+            Assert.False(message.HasDefaultUint32);
+            Assert.False(message.HasDefaultUint64);
+        }
+
+        [Test]
+        public void FieldPresence()
+        {
+            var message = new TestAllTypes();
+
+            Assert.False(message.HasOptionalBool);
+            Assert.False(message.OptionalBool);
+
+            message.OptionalBool = true;
+
+            Assert.True(message.HasOptionalBool);
+            Assert.True(message.OptionalBool);
+
+            message.OptionalBool = false;
+
+            Assert.True(message.HasOptionalBool);
+            Assert.False(message.OptionalBool);
+
+            message.ClearOptionalBool();
+
+            Assert.False(message.HasOptionalBool);
+            Assert.False(message.OptionalBool);
+
+            Assert.False(message.HasDefaultBool);
+            Assert.True(message.DefaultBool);
+
+            message.DefaultBool = false;
+
+            Assert.True(message.HasDefaultBool);
+            Assert.False(message.DefaultBool);
+
+            message.DefaultBool = true;
+
+            Assert.True(message.HasDefaultBool);
+            Assert.True(message.DefaultBool);
+
+            message.ClearDefaultBool();
+
+            Assert.False(message.HasDefaultBool);
+            Assert.True(message.DefaultBool);
+        }
+
+        [Test]
+        public void RequiredFields()
+        {
+            var message = new TestRequired();
+            Assert.False(message.IsInitialized());
+
+            message.A = 1;
+            message.B = 2;
+            message.C = 3;
+
+            Assert.True(message.IsInitialized());
+        }
+
+        [Test]
+        public void RequiredFieldsInExtensions()
+        {
+            var message = new TestAllExtensions();
+            Assert.True(message.IsInitialized());
+
+            message.SetExtension(TestRequired.Extensions.Single, new TestRequired());
+
+            Assert.False(message.IsInitialized());
+
+            var extensionMessage = message.GetExtension(TestRequired.Extensions.Single);
+            extensionMessage.A = 1;
+            extensionMessage.B = 2;
+            extensionMessage.C = 3;
+
+            Assert.True(message.IsInitialized());
+
+            message.GetOrRegisterExtension(TestRequired.Extensions.Multi);
+
+            Assert.True(message.IsInitialized());
+
+            message.GetExtension(TestRequired.Extensions.Multi).Add(new TestRequired());
+
+            Assert.False(message.IsInitialized());
+
+            extensionMessage = message.GetExtension(TestRequired.Extensions.Multi)[0];
+            extensionMessage.A = 1;
+            extensionMessage.B = 2;
+            extensionMessage.C = 3;
+
+            Assert.True(message.IsInitialized());
+
+            message.SetExtension(UnittestExtensions.OptionalBoolExtension, true);
+
+            Assert.True(message.IsInitialized());
+
+            message.GetOrRegisterExtension(UnittestExtensions.RepeatedBoolExtension).Add(true);
+
+            Assert.True(message.IsInitialized());
+        }
+
+        [Test]
+        public void RequiredFieldInNestedMessageMapValue()
+        {
+            var message = new TestRequiredMap();
+            message.Foo.Add(0, new TestRequiredMap.Types.NestedMessage());
+
+            Assert.False(message.IsInitialized());
+
+            message.Foo[0].RequiredInt32 = 12;
+
+            Assert.True(message.IsInitialized());
+        }
+
+        [Test]
+        public void RoundTrip_Groups()
+        {
+            var message = new TestAllTypes
+            {
+                OptionalGroup = new TestAllTypes.Types.OptionalGroup
+                {
+                    A = 10
+                },
+                RepeatedGroup =
+                {
+                    new TestAllTypes.Types.RepeatedGroup { A = 10 },
+                    new TestAllTypes.Types.RepeatedGroup { A = 20 },
+                    new TestAllTypes.Types.RepeatedGroup { A = 30 }
+                }
+            };
+
+            byte[] bytes = message.ToByteArray();
+            TestAllTypes parsed = TestAllTypes.Parser.ParseFrom(bytes);
+            Assert.AreEqual(message, parsed);
+        }
+
+        [Test]
+        public void RoundTrip_ExtensionGroups()
+        {
+            var message = new TestAllExtensions();
+            message.SetExtension(UnittestExtensions.OptionalGroupExtension, new OptionalGroup_extension { A = 10 });
+            message.GetOrRegisterExtension(UnittestExtensions.RepeatedGroupExtension).AddRange(new[]
+            {
+                new RepeatedGroup_extension { A = 10 },
+                new RepeatedGroup_extension { A = 20 },
+                new RepeatedGroup_extension { A = 30 }
+            });
+
+            byte[] bytes = message.ToByteArray();
+            TestAllExtensions extendable_parsed = TestAllExtensions.Parser.WithExtensionRegistry(new ExtensionRegistry() { UnittestExtensions.OptionalGroupExtension, UnittestExtensions.RepeatedGroupExtension }).ParseFrom(bytes);
+            Assert.AreEqual(message, extendable_parsed);
+        }
+
+        [Test]
+        public void RoundTrip_NestedExtensionGroup()
+        {
+            var message = new TestGroupExtension();
+            message.SetExtension(TestNestedExtension.Extensions.OptionalGroupExtension, new TestNestedExtension.Types.OptionalGroup_extension { A = 10 });
+
+            byte[] bytes = message.ToByteArray();
+            TestGroupExtension extendable_parsed = TestGroupExtension.Parser.WithExtensionRegistry(new ExtensionRegistry() { TestNestedExtension.Extensions.OptionalGroupExtension }).ParseFrom(bytes);
+            Assert.AreEqual(message, extendable_parsed);
+        }
+    }
+}