How to test a Firebase task on Android?

Question

Now I am trying to test it using JUnit4, but I am getting

java.lang.IllegalStateException:
    Must not be called on the main application thread

at com.google.android.gms.common.internal.zzab.zzhj(Unknown Source)
at com.google.android.gms.common.internal.zzab.zzate(Unknown Source)
at com.google.android.gms.tasks.Tasks.await(Unknown Source)
at com.example.tasks.GetUserProfileTest.then(GetUserProfileTest.java:18)
    <27 internal calls>

Process finished with exit code 255

I've created a Continuation task that performs an operation on Firebase Realtime Database.

public class GetUserProfile implements Continuation<String, Task<Profile>>,
        ValueEventListener {

    private TaskCompletionSource<Profile> mTaskCompletionSource;
    private DatabaseReference mDatabase;

    public GetUserProfile() {
        mTaskCompletionSource = new TaskCompletionSource();
        mDatabase = FirebaseDatabase.getInstance().getReference();
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        mDatabase.removeEventListener(this);
        mTaskCompletionSource.setException(databaseError.toException());
    }

    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        mDatabase.removeEventListener(this);
        mTaskCompletionSource.setResult(dataSnapshot.getValue(Profile.class));
    }

    @Override
    public Task<Profile> then(Task<String> task) {
        mDatabase.child(task.getResult()).addValueEventListener(this);
        return mTaskCompletionSource.getTask();
    }
}

and unit test for it:

public class GetUserProfileTest {
    @Test
    public void then() throws Exception {
        Task<Profile> task = Tasks.<String>forResult("17354686546")
            .continueWithTask(new GetUserProfile());

        try {
            Profile profile = Tasks.await(task);
            assertEquals(profile.getEmail(), "john.connor@email.com");
        } catch (ExecutionException e) {
            fail(e.getMessage());
        } catch (InterruptedException e) {
            fail(e.getMessage());
        }
    }
}

Is there a simple way of testing tasks without using handlers or CountDownLatch?

Answer 1

public class GetUserProfileTest {
    @Test
    public void then() throws Exception {
        try {
            Task<String> previousTask = Tasks.forResult("17354686546");
            GetUserProfile continuation = new GetUserProfile();
            Profile profile = continuation
                    .then(previousTask)
                    .getResult();

            assertEquals(profile.getEmail(), "john.connor@email.com");
        } catch (ExecutionException e) {
            fail(e.getMessage());
        } catch (InterruptedException e) {
            fail(e.getMessage());
        }
    }
}