public void Should_Get_Customer_Orders_And_Return_Success_Status_Code() { // Arrange Guid _guid = Guid.NewGuid(); string customerId = _guid.ToString(); Mock <IOrderService> mockOrderService = new Mock <IOrderService>(); mockOrderService.Setup(o => o.GetCustomerOrders(It.IsAny <string>())) .Returns(It.IsAny <IEnumerable <Order> >()); OrderApiController controller = new OrderApiController(mockOrderService.Object); // Act var result = controller.GetCustomerOrders(customerId); var checkresult = result as ObjectResult; // Assert Assert.IsNotNull(checkresult); Assert.AreEqual(200, checkresult.StatusCode); }