Unit testing a Web API controller

Question

I am fairly new to unit testing and I am trying to create a unit test for a Web API contoller that I have created which returns a list of brands.

My Web API controller Get() method looks like this:

[HttpGet("/api/Brands/Get", Name = "GetBrands")]
public async Task<IActionResult> Get()
{
    var brands = await _brandsService.GetAll(null, "Image");
    return Json(brands);
}

The generic service method looks like this:

public async Task<List<T>> GetAll(
    Func<IQueryable<T>, 
    IOrderedQueryable<T>> orderBy = null, 
    string includeProperties = null)
{
    return await _genericRepository.GetAll(orderBy, includeProperties);
}

and the generic repo method looks like this:

public async Task<T> Get<TKey>(Expression<Func<T, bool>> filter = null, string includeProperties = "", bool noTracking = false)

{
    includeProperties = includeProperties.Trim() ?? string.Empty;
    IQueryable<T> query = Context.Set<T>();

    if (noTracking)
    {
        query.AsNoTracking();
    }

    if (filter != null)
    {
        query = query.Where(filter);
    }

    foreach (var includeProperty in includeProperties.Split
        (new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
    {
        query = query.Include(includeProperty);
    }

    return await query.SingleOrDefaultAsync();
}

This is working and I am returning a list of brands from the database.

Now I tried to create a Unit test for this:

[SetUp]
public void Setup()
{
    Brands = new List<Brand>
    {
        new Brand
        {
            Id = 1,
            Name = "Adidas",
            ImageId = 1
        },
        new Brand
        {
            Id = 2,
            Name = "Nike",
            ImageId = 2
        },
        new Brand
        {
            Id = 3,
            Name = "Puma",
            ImageId = 3
        }
    };
}

[Test]
public async Task Get_ReturnsAAListOfBrands()
{
    //Arrange
    var mockService = new Mock<IGenericService<Brand>>();
    mockService.Setup(repo => repo.GetAll(null, null)).Returns(Task.FromResult(Brands));
    var controller = new BrandsController(mockService.Object);

    //Act
    var result = await controller.Get();
    //Assert
}

however the result is always null. Am I testing this correctly or do I need to change my unit test code to verify that the mock service has three items stored?

Answer 1

You need to configure the setup to expect a particular behavior or argument for the test.

In this case using the It.IsAny<T>() to tell the set up what to expect in terms of arguments will allow the test to flow as desired.

Given that the GetAll method requires two parameters of Func<IQueryable<T>, IOrderedQueryable<T>> and string, the setup configures what to do based on the values entered for those parameters.

[Test]
public async Task Get_ReturnsAAListOfBrands() {
    //Arrange
    var mockService = new Mock<IGenericService<Brand>>();
    mockService
        .Setup(repo => repo.GetAll(It.IsAny<Func<IQueryable<Brand>, IOrderedQueryable<Brand>>>(), It.IsAny<string>()))
        .ReturnsAsync(Brands);
    var controller = new BrandsController(mockService.Object);

    //Act
    var result = await controller.Get();
    //Assert
    //...
}

Take a look at the Moq Quickstart for a better understanding of how to use this mocking framework