private void DoTestGenericRetval <T>(T expectedRetval)
        {
            var handler = CreateClass("MyService", "GenericRetval")(new[] { typeof(T) });

            var retvalCodec = codecContainer.GetManualCodecFor <T>();

            var expectedData = new byte[retvalCodec.CalculateSize(expectedRetval)];

            fixed(byte *pData = expectedData)
            {
                var p = pData;

                retvalCodec.Encode(ref p, expectedRetval);
            }

            service.GenericRetval <T>().ReturnsForAnyArgs(expectedRetval);

            var result = handler.Handle(service, null, 0).Result;

            var serviceCall = service.ReceivedCalls().Last();

            Assert.That(serviceCall.GetMethodInfo(), Is.EqualTo(typeof(IGlobalService).GetMethod("GenericRetval").MakeGenericMethod(new[] { typeof(T) })));
            Assert.That(result, Is.EquivalentTo(expectedData));
        }