Testing with MVP: Exception

- [Narrator] Now we will test the togFavorites function without loading a recipe first. If you go to the Presenter, scroll down, and look at the togFavorite function. Remember when we were writing it, I was like, "Oh! If the recipe is null, it's going to be bad." So let's try that. Let's actually try the case when we have a presenter but we have no code, no recipe yet. So recipe is null, and then in toggleFavorite we will try to read this ID.

Go back to the test. Once again, when you're on the class itself, when you press Command+Shift+T, you can switch to the associated test. We'll add a new test method, @Test to indicate that it is a test method, and then public void, we will call it togglewithoutLoad. Since we have initialized the presenter in the setup method, all we need to do here is to code toggle.

So presenter.toggleFavorite. How are we going to verify that it actually throws an exception? Well one thing you can do is to just run the test. So let's do that. Click on the green triangle and press run. So here in the test it threw an illegal state exception, which is what we want it to do if we try to toggle a favorite without first loading a recipe. However, this is the failing test case.

We don't actually want to have a test case where we expect it to fail. Fortunately, in the JUnit framework, we can specify and expect an exception. All you need to do is to go to the test annotation on line 34 and then @expected equal, in our case, IllegalStateException, dot class. Now, when we run the test, it passes.

This means that JUnit ran the test method and verified that it is throwing IllegalStateException, and therefore calling it a passing test. Next, we will test the case when we are actually loading a recipe.