[TestMethod] // test stubs public void Get_WithNullId_ShouldReturnObjectResult() // ServiceMethodToBeTest_ExpectedInput_ExpectedBehavior() { // arrange mockRepo .Setup( r => r.Retrieve() ) .Returns(new List <Sample>()); // act var result = sut.GetSample(null); // assert mockRepo .Verify( r => r.Retrieve(), Times.Once ); Assert.IsInstanceOfType(result, typeof(OkObjectResult)); }