有没有一种简单的方法可以在使用FragmentScenario的测试中注入匕首模拟？

Question

I've just come across FragmentScenario and would like to use it to test Fragments in isolation. But my app uses Dagger and I can't find a good way to run the FragmentScenario and get mocked fields into the fragment under test. My current test setup launches an Activity and uses DaggerMock to inject mockito mock dependencies. However I would really like to add isolated fragment tests.

Is it possible to do this with FragmentScenario? Will it be supported sometime soon?

I've seen this article suggesting a solution but I don't like the idea of having to open fragment classes just for testing https://proandroiddev.com/testing-dagger-fragments-with-fragmentscenario-155b6ad18747

Answer 1

I used a solution for a similar scenario at activity level, please see How do you re-inject an android object, (Service, Activity...) being injected into by an AndroidInjector, into other objects? for reference.

How can we apply this solution

consider:

class MyFragment extends Fragment
{
 ....
}

make a subclass:

class MyFragmentInjector extends MyFragment
{
   public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup 
      container,  @Nullable Bundle savedInstanceState) {
      initialiseDependencies();
      super.onCreateView(inflater, container, savedInstanceState);
   }

   public void initialiseDependencies()
   {
      DaggerMyFragmentComponent.Factory.create().inject(this);
   }
}

Make a test implementation subclass

class MyFragmentInjectorTestImpl extends MyFragment
{
   public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup 
      container,  @Nullable Bundle savedInstanceState) {
      initialiseDependencies();
      super.onCreateView(inflater, container, savedInstanceState);
   }

   public void initialiseDependencies()
   {
      DaggerMyFragmentTestComponent.Factory.create().inject(this);
   }
}

Your test component would contain all of your mocked modules to replace your real ones:

This means that to run your test you would have:

FragmentScenario.launch(MyFragmentInjectorTestImpl.class);

and use

 FragmentScenario.FragmentAction<MyFragmentInjectorTestImpl> mAction;

but since MyFragmentInjectorTestImpl is still and instance of MyFragment you will be testing MyFragment with your mock dependencies injected.

The problem is that all of this initialisation has to be done at a subclass level (because it needs to inject the dependencies into its parent), which is not ideal, if you have many fragments it seems like there are a lot of unnecessary extra class implementations but it means that your MyFragment class with your real code is somewhat cleaner.