How to test protected properties?

[MiBuena]

We have a partial class which contains the code for the Blazor view.

In it we have collections with items which we display in the view. The collections are protected properties and are used only in the view.

What is the right way to test them?

Should we just get the markup where they are rendered and check that it contains the necessary information?

Or should we try to extract them in some way from the component?

eg:

public partial class ShoppingList
{
    protected List<ItemViewModel> Items { get; set; } = new List<ItemViewModel>();
}

[egil]

Hi @MiBuena,

This is less of a bUnit question and more a question of testing strategy in general.

My gut feeling is that if something is non-public, its an implementation detail that you should not be writing your tests against. If you do, you tie your tests very tightly to an implementation detail that you might want to change later without breaking your tests. Internal refactoring of a component under test that does NOT change its output or observable behavior should no be breaking tests.

If it is an important business requirement that the Items list contains certain items, I would instead ask why it is protected in the first place? If it is important, then it likely also needs to be public so others can access it. It can always be an IReadOnlyList<ListViewModel> if it should be read only.

If this is indeed an implementation detail, I would use the one of approaches described on https://bunit.egilhansen.com/docs/verification/verify-markup to verify that the component renders the appropriate markup for the input.

Hope this helps, Egil.

[MiBuena]

Thank you for your detailed reply, @egil !

Reading your answer - my thoughts go the same direction.

This collection is only used in the razor view. So it even can be made private.

If something can be made private - my feeling says it is probably an implementation detail.

But I see in the examples for dependency injection in the documentation here that the Forecasts collection is actually made public and it is specifically tested. Which confused me a bit.

// Assert that service is injected
Assert.NotNull(cut.Instance.Forecasts);

Can you please explain more on this? Is the Forecases collection here public just as an example or? Is there a specific reason to make it public in this case? Since as I see the Forecases collection is not used anywhere else in this case.

[egil]

In this particular case it is just to showcase dependency injection. Normally there is no particular reason to have it public as others they needed could simply get it the same way, through DI.

[MiBuena]

Thank you, @egil !

In such a case, I will keep my collection private and test only against the markup - as you suggested.

Thank you again for your attention!