public void Attachments_GetData() { // Set test GetData method w/o parameters request.Setup(m => m.Get <Stream>("attachments/666/data", null)).Returns(new MemoryStream()); // Test Get method var result = attachmentsProxy.GetData(666); // Verify test Assert.IsNotNull(result); Assert.IsTrue(result.IsSuccessful); Assert.IsNotNull(result.Data); }