public async void Should_return_bad_request()
            {
                // Arrange
                var nationality = new Nationality
                {
                    Name = "China"
                };

                ControllerUnderTest.ModelState.TryAddModelError("key", "there is an error");


                // Act
                var result = await ControllerUnderTest.AddNationality(nationality);

                // Assert
                var badRequest = Assert.IsType <BadRequestObjectResult>(result);

                Assert.IsType <SerializableError>(badRequest.Value);
            }
            public async void Should_return_OK()
            {
                // Arrange
                var nationality = new Nationality
                {
                    Name = "England"
                };
                var result = new Result();

                NationalityServiceMock
                .Setup(x => x.AddNationalityAsync(nationality))
                .ReturnsAsync(result);

                // Act
                var requestResult = await ControllerUnderTest.AddNationality(nationality);

                // Assert
                var okResult = Assert.IsType <OkObjectResult>(requestResult);

                Assert.Same(result, okResult.Value);
            }
            public async void Should_return_error_with_message()
            {
                // Arrange
                var nationality = new Nationality
                {
                    Name = "Austria"
                };
                var result = new Result();

                result.AddError("there was an error");
                NationalityServiceMock
                .Setup(x => x.AddNationalityAsync(nationality))
                .ReturnsAsync(result);

                // Act
                var requestResult = await ControllerUnderTest.AddNationality(nationality);

                // Assert
                var okResult = Assert.IsType <OkObjectResult>(requestResult);

                Assert.Same(result, okResult.Value);
            }