Good Unit Tests when ReSharper bugs for null checks

Question

I have the latest version of ReSharper installed and I am trying to write a Unit Test for my MVC controller. I need the Unit Test to:

Ensure the ViewModel passed to the View is of the correct type.

So here is what I have at the moment:

public void Create_HasCorrectViewModelType()
{
    // arrange
    var controller = new DraftController(_draftFacade);
    // act
    var viewResult = controller.Create() as ViewResult;
    var viewModel = viewResult.Model as DraftViewModel;
    // assert
    Assert.IsInstanceOfType(viewModel.GetType(), typeof(DraftViewModel));
}

I have issues with this, and would like to know your thoughts on the matter.

1. the arrange makes sense. I am arranging / setting up my controller.
2. Only the first line in the act seems logical to me. But me trying to grab the ViewModel isn't really an Act is it? Sounds like // arrange again!
3. ReSharper complains that I am not doing null checks on viewResult and viewModel.

I can go with ReSharper's recommendation, then my test becomes:

public void Create_HasCorrectViewModelType()
{
    // arrange
    var controller = new DraftController(_draftFacade);
    // act
    var viewResult = controller.Create() as ViewResult;
    var viewModel = viewResult?.Model as DraftViewModel;
    // assert
    if (viewModel != null) Assert.IsInstanceOfType(viewModel.GetType(), typeof(DraftViewModel));
}

Now ReSharper is happy, but then my Unit Test don't seem clean anymore! I feel like there are too many paths that can be taken for that one unit test.

Anyone else bugged by this? What can I do to improve this? Or is this the best I'm going to get?

Any help would be greatly appreciated.

Answer 1

Asserting

if (viewModel != null) Assert.IsInstanceOfType(viewModel.GetType(), typeof(DraftViewModel));

You should use another assert and not an if

Assert.IsNotNull(viewModel);

Resharper even suggests this option:

Test name

Create_DraftFacade_ViewResultWithDraftViewModel

You might also want to reconsider the naming of your tests. Usually we use this pattern

TestedMethod/Property_TestData/Case_ExpectedResult

Answer 2

If controller.Create() is always creating ViewResult you must use explicit cast

var viewResult = (ViewResult)controller.Create();

else you must write another test for controller.Create().

The assertion code var viewModel = viewResult.Model as DraftViewModel; are using as, if the conversion isn't possible, as returns null so instead of IsInstanceOfType use IsNotNUll.

By the way, I can't get the act of your test by seeing your method name and I recommend you to read this article.