Testing. Code example for c# | Mario Codes

The following are code examples to test several scenarios.

(check this project to see more testing code examples)

Test a controller

GivenCorrectDate_WhenGetAvailability_ThenAssertCorrectReturnValue asserts a controller returns 200 when everything goes right
GivenWrongDate_WhenGetAvailability_ThenAssert400ReturnValue assert a controller returns 400 with specific error message
GivenServiceThrowsException_WhenReserveSlot_ThenAssertExceptionCaught assert method throws an exception, but it is correctly caught

public class SlotsControllerTest
{
	// class we're testing
	private SlotsController _controller;

	private Mock<ISlotsService> _slotsServiceMock;
	
	private Mock<IOptions<CoreConfig>> _iOptConfigMock;
	private Mock<CoreConfig> _configMock;
	
	[SetUp]
	public void SetUp()
	{
		_configMock = new Mock<CoreConfig>();
		_iOptConfigMock = new Mock<IOptions<CoreConfig>>();
		_iOptConfigMock.Setup(iOpt => iOpt.Value).Returns(_configMock);
		
		_slotsServiceMock = new Mock<ISlotsService>();
		_controller = new SlotsController(_slotsServiceMock.Object, _iOptConfigMock.Object);
	}

[Test]
public async Task GivenWrongDate_WhenGetAvailability_ThenAssert400ReturnValue()
{
	// given
	string date = "";
	string errorMessage = "oh no! something went wrong!";
	
	var errorMessages = new ErrorMessages
	{
		GeneralErrorMessage = errorMessage
	};
	
	_configMock.Setup(conf => conf.GeneralErrorMessage).Returns(errorMessage);
	
	// when
	var result = await _controller.GetAvailability(date) as BadRequestObjectResult;
	
	// then
	result.Should().NotBeNull();
	result.StatusCode.Should().Be(400);
	result.Value.ToString().Should().Contain(errorMessage);
}

[Test]
public async Task GivenCorrectDate_WhenGetAvailability_ThenAssertCorrectReturnValue()
{
	// given
	string date = "20241012";
	var parsedDate = new DateOnly(2024, 10, 12);
	
	string dateFormat = "yyyyMMdd";
	_configMock.Setup(conf => conf.InputDateFormat).Returns(dateFormat);
	
	var dto = new WeekAvailabilityResponse();
	_slotsServiceMock.Setup(service => service.GetWeekSlotsAsync(parsedDate)).ReturnsAsync(dto);
	
	// when
	var result = await _controller.GetAvailability(date) as OkObjectResult;
	
	// then
	result.Should().NotBeNull();
	result.StatusCode.Should().Be(200);
	result.Value.Should().Be(dto);
}

[Test]
public async Task GivenServiceThrowsException_WhenReserveSlot_ThenAssertExceptionCaught()
{
	// given
	var request = new ReserveSlotRequest();

	string errorMessage = "error when throw exception";
	var errorMessages = new ErrorMessages
	{
		GeneralErrorMessage = errorMessage
	};
	
	_configMock.Setup(conf => conf.GeneralErrorMessage).Returns(errorMessage);
	_slotsServiceMock.Setup(service => service.ReserveSlotsAsync(parsedDate)).ThrowAsync(new HttpRequestException(errorMessage));

	// when
	var result = await _controller.ReserveSlot(request) as BadRequestObjectResult
	
	// then
	result.Should().NotBeNull();
	result.StatusCode.Should().Be(400);
	result.Value.ToString().Should().Contain(errorMessage);
}

General tests

This is a test to check an exception is thrown for a non-async method.

The method .WithMessage("*null payload*") works as a like. Any string that contains null payload will trigger as true.

[Test]
public async Task GivenNullPayload_WhenSetupPost_ThenAssertExceptionIsThrown
{
	// given
	string url = "http://somethingsomething.com"
	string nullPayload = null;
	
	// when
	Action result = () => _service.SetUpPost(url, nullPayload);
	
	// then
	result.Should().Throw<ArgumentNullException>().WithMessage("*null payload*");
}

This is the example for an async method.

[Test]
public async Task GivenNullPayload_WhenSetupPostAsync_ThenAssertExceptionIsThrown
{
	// given
	string url = "http://somethingsomething.com";
	string nullPayload = null;
	
	// when
	Func<Task> result = () => _service.SetUpPostAsync(url, nullPayload);
	
	// then
	await result.Should().ThrowAsync<InvalidOperationException>().WithMessage("*null payload*");
}