public void Projects_AddAttachment() { var anAttachment = new Attachment { Id = 0 }; // Set test Create method w/o parameters request.Setup(m => m.Post <Response <Attachment> >("projects/666/attachments", anAttachment, null)).Returns(new Response <Attachment> { Data = new Attachment { Id = 1234 } }); // Test Get method var result = projectsProxy.AddAttachment(666, anAttachment); // Verify test Assert.IsNotNull(result); Assert.IsTrue(result.IsSuccessful); Assert.AreEqual(1234, result.Data.Id); }