increase test coverage
diff --git a/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
index 5f90c94..1abed60 100644
--- a/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
+++ b/csharp/src/Google.Protobuf.Test/GeneratedMessageTest.Proto2.cs
@@ -344,6 +344,8 @@
                 }

             };

 

+            MessageParsingHelpers.AssertWritingMessage(message);

+

             MessageParsingHelpers.AssertRoundtrip(Proto2.TestAllTypes.Parser, message);

         }

 

@@ -359,6 +361,8 @@
                 new RepeatedGroup_extension { A = 30 }

             });

 

+            MessageParsingHelpers.AssertWritingMessage(message);

+

             MessageParsingHelpers.AssertRoundtrip(

                 TestAllExtensions.Parser.WithExtensionRegistry(new ExtensionRegistry() { UnittestExtensions.OptionalGroupExtension, UnittestExtensions.RepeatedGroupExtension }),

                 message);

@@ -370,6 +374,8 @@
             var message = new TestGroupExtension();

             message.SetExtension(TestNestedExtension.Extensions.OptionalGroupExtension, new TestNestedExtension.Types.OptionalGroup_extension { A = 10 });

 

+            MessageParsingHelpers.AssertWritingMessage(message);

+            

             MessageParsingHelpers.AssertRoundtrip(

                 TestGroupExtension.Parser.WithExtensionRegistry(new ExtensionRegistry() { TestNestedExtension.Extensions.OptionalGroupExtension }),

                 message);