Unit testing controller methods which return IActionResult

Question

I'm in the process of building an ASP.NET Core WebAPI and I'm attempting to write unit tests for the controllers. Most examples I've found are from the older WebAPI/WebAPI2 platforms and don't seem to correlate with the new Core controllers.

My controller methods are returning IActionResults. However, the IActionResult object only has a ExecuteResultAsync() method which requires a controller context. I'm instantiating the controller manually, so the controller context in this instance is null, which causes an exception when calling ExecuteResultAsync. Essentially this is leading me down a very hacky path to get these unit tests to successfully complete and is very messy. I'm left wondering that there must be a more simple/correct way of testing API controllers.

Also, my controllers are NOT using async/await if that makes a difference.

Simple example of what I'm trying to achieve:

Controller method:

[HttpGet(Name = "GetOrdersRoute")]
public IActionResult GetOrders([FromQuery]int page = 0)
{
     try
     {
        var query = _repository.GetAll().ToList();

        int totalCount = query.Count;
        int totalPages = (int)Math.Ceiling((double)totalCount / pageSize) - 1;
        var orders = query.Skip(pageSize * page).Take(pageSize);

        return Ok(new
        {
           TotalCount = totalCount,
           TotalPages = totalPages,

           Orders = orders
        });
     }
     catch (Exception ex)
     {
        return BadRequest(ex);
     }
}

Unit test:

[Fact]
public void GetOrders_WithOrdersInRepo_ReturnsOk()
{
     // arrange
     var controller = new OrdersController(new MockRepository());

     // act
     IActionResult result = controller.GetOrders();

     // assert
     Assert.Equal(HttpStatusCode.OK, ????);
}

Solution 1

Assuming something like the

public IActionResult GetOrders() {
    var orders = repository.All();
    return Ok(orders);
}

the controller in this case is returning an OkObjectResult class.

Cast the result to the type of what you are returning in the method and perform your assert on that

[Fact]
public void GetOrders_WithOrdersInRepo_ReturnsOk() {
    // arrange
    var controller = new OrdersController(new MockRepository());

    // act
    var result = controller.GetOrders();
    var okResult = result as OkObjectResult;

    // assert
    Assert.IsNotNull(okResult);
    Assert.AreEqual(200, okResult.StatusCode);
}

Solution 2

You can also do cool things like:

    var result = await controller.GetOrders();//
    var okResult = result as ObjectResult;

    // assert
    Assert.NotNull(okResult);
    Assert.True(okResult is OkObjectResult);
    Assert.IsType<TheTypeYouAreExpecting>(okResult.Value);
    Assert.Equal(StatusCodes.Status200OK, okResult.StatusCode);

Thanks

Solution 3

Other answers adviced to cast to ObjectResult, but its work only if you return OkObjectResult \ NotFoundObjectResult \ etc. But server could return NotFound\ OkResult which derived from StatusCodeResult.

For example:

public class SampleController : ControllerBase
{
    public async Task<IActionResult> FooAsync(int? id)
    {
        if (id == 0)
        {
            // returned "NotFoundResult" base type "StatusCodeResult"
            return NotFound();
        }

        if (id == 1)
        {
            // returned "StatusCodeResult" base type "StatusCodeResult"
            return StatusCode(StatusCodes.Status415UnsupportedMediaType);
        }

        // returned "OkObjectResult" base type "ObjectResult"
        return new OkObjectResult("some message");
    }
}

I looked at the implementation of all these methods and found that they are all inherited from the IStatusCodeActionResult interface. It seems like this is the most base type that contains StatusCode:

private SampleController _sampleController = new SampleController();

[Theory]
[InlineData(0, StatusCodes.Status404NotFound)]
[InlineData(1, StatusCodes.Status415UnsupportedMediaType)]
[InlineData(2, StatusCodes.Status200OK)]
public async Task Foo_ResponseTest(int id, int expectedCode)
{
    var actionResult = await _sampleController.FooAsync(id);
    var statusCodeResult = (IStatusCodeActionResult)actionResult;
    Assert.Equal(expectedCode, statusCodeResult.StatusCode);
}

Comments

[Nkosi]

Show the GetOrders method. what are you returning in that method. cast the result to the type of what you are returning in the method and perform your assert on that.

[Squirrelkiller]

Hi again Nkosi :) Can I somehow compare the whole result object to an expected one, so I can check both return code and object? Right now, Assert.AreEqual<IActionResult>(actual, expected) doesn't seem to work. Edit: The object is a string. Do I have to make to Asserts?

[Nkosi]

@Squirrelkiller that would be because they are two separate instances. You could extract the object from the result and make your comparison on that provided you control both.

[Nkosi]

@Squirrelkiller for example Assert.AreEquan(myObject, okResult.Value); where myObject is assumed to be what was returned from your mock and passed to Ok() in the controller action.

[Mauro Bilotti]

The problem with this appears when you're returning just Ok() with no content and it's retuning an OkResult instead an OkObjectResult.

[Cedervall]

When casting to an OkObjectResult wouldn't it always have a status code of 200?