I'm new to unit testing and have been working on some simple tests but, am having issues trying to use count() to check the returned data.

Here is my test

        [Fact]
        public async void Should_Call_Controller_Get_Return_200()
        {
            // Arrange
            var context = new HotelListingDbContext(dbContextOptions);
            var countriesService = new CountriesRepository(context, _mapper);
            var controller = new CountriesController(_mapper, countriesService);

            // Act
            var data = await controller.GetCountries();

            // Assert
            Assert.IsType<OkObjectResult>(data.Result);  
            data.Result.Should().NotBeNull();
            data.Value.Count.Should().Be(3);  // <<< Object reference not set to an instance of an object.
        }

When I debug, data contains 3 items as per below:

Could someone please explain what I should do? I can see that Value is null.

I have tried data.Result.Value.Count but the error states: "ActionResult does not contain a definition for Value" which is confusing me. I have also looked at using Assert.Collection but not sure this is relevant.

I have been looking at the MS docs for unit testing trying to apply it to my project, but am stuck here. I guess it's something to do with the ActionResult and a step I am missing.

CodePudding user response：

In order to access the derived type properties with a specific type you should first cast the result to that specific type.

Considering the fact that you are using fluent assertions you can use something similar to:

data.Result.Should().BeOfType<OkObjectResult>()
    .Which.Value.Should().BeOfType<List<GetCountryDTO>>()
    .Which.Should().HaveCount(3);

Hope it helps,