How to test a Fragment using Espresso

Question

I have an Android fragment that I want to test. I created a test activity to which I add this fragment and run some Espresso tests.

However, Espresso does not find any of the views inside the fragment. It dumps the view hierarchy and it is all empty.

I do not want to use the actual parent activity. I want to just test this fragment in isolation. Has anyone done this? Is there a sample that has a similar code?

@RunWith(AndroidJUnit4.class)
class MyFragmentTest {
    @Rule
    public ActivityTestRule activityRule = new ActivityTestRule<>(
    TestActivity.class);

    @Test
    public void testView() {
       MyFragment myFragment = startMyFragment();
       myFragment.onEvent(new MyEvent());
       // MyFragment has a recyclerview. 
       //OnEvent is EventBus callback that in this test contains no data.
       //I want the fragment to display empty list text and hide the recyclerView
       onView(withId(R.id.my_empty_text)).check(matches(isDisplayed()));
       onView(withId(R.id.my_recycler)).check(doesNotExist()));
    }

    private MyFragment startMyFragment() {
         FragmentActivity activity = (FragmentActivity) activityRule.getActivity();
    FragmentTransaction transaction = activity.getSupportFragmentManager().beginTransaction();
    MyFragment myFragment = new MyFragment();
    transaction.add(myFragment, "myfrag");
    transaction.commit();
    return myFragment;
    }
}

Solution 1

I will do in following way Create a ViewAction as follows:

public static ViewAction doTaskInUIThread(final Runnable r) {
    return new ViewAction() {
        @Override
        public Matcher<View> getConstraints() {
            return isRoot();
        }

        @Override
        public String getDescription() {
            return null;
        }

        @Override
        public void perform(UiController uiController, View view) {
            r.run();
        }
    };
}

Then use below to launch code which should be run in UI Thread

onView(isRoot()).perform(doTaskInUIThread(new Runnable() {
        @Override
        public void run() {
            //Code to add your fragment or anytask that you want to do from UI Thread
        }
    }));

below is an example of test case adding fragment view hierarchy

    @Test
public void testSelectionOfTagsAndOpenOtherPage() throws Exception{

    Runnable r = new Runnable() {
        @Override
        public void run() {
            //Task that need to be done in UI Thread (below I am adding a fragment)

        }
    };
    onView(isRoot()).perform(doTaskInUIThread(r));

}

Solution 2

public class VoiceFullScreenTest {
    @Rule
    public ActivityTestRule activityRule = new ActivityTestRule<>(
            TestActivity.class);

    @Test
    public void fragment_can_be_instantiated() {
        activityRule.getActivity().runOnUiThread(new Runnable() {
            @Override
            public void run() {
                VoiceFragment voiceFragment = startVoiceFragment();
            }
        });
        // Then use Espresso to test the Fragment
        onView(withId(R.id.iv_record_image)).check(matches(isDisplayed()));
    }

    private VoiceFragment startVoiceFragment() {
        TestActivity activity = (TestActivity) activityRule.getActivity();
        FragmentTransaction transaction = activity.getSupportFragmentManager().beginTransaction();
        VoiceFragment voiceFragment = new VoiceFragment();
        transaction.add(voiceFragment, "voiceFragment");
        transaction.commit();
        return voiceFragment;
    }


}

You can start your fragment from UI thread as mentioned above.

Solution 3

You can use the androidx.fragment:fragment-testing library. Launching the fragment in your test method is as simple as:

val fragmentArgs = Bundle()
androidx.fragment.app.testing.launchFragmentInContainer<MyFragment>(fragmentArgs)

You can find more information about this library here.

Solution 4

You can use FragmentTestRule.

Instead of the regular ActivityTestRule you must use:

@Rule
public FragmentTestRule<?, FragmentWithoutActivityDependency> fragmentTestRule =
    FragmentTestRule.create(FragmentWithoutActivityDependency.class);

You can find more details in this blog post.

Solution 5

You've probably forgot to inject the fragment in the view hierarchy. Try defining the holder container for your fragment in the TestActivity layout (like a FrameLayout with id fragment_container) and then instead of just add(myFragment, "tag"), use the add(R.id.fragment_container, myFragment, "tag") (this method). I guess you could use the replace method with the same signature as well.

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Comments

[greenrobo]

I tried this method (using add(id, fragment, tag)) but that did not help. I suspect that this is because of multiple threads interacting. Espresso somehow does not like this.