JUnit testing on class with firebase

Question

I'm trying to JUnit test this class:

public class WeekListActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {

    private ArrayList<String> weekList = new ArrayList<>();
    private ArrayAdapter<String> adapter;


    ListView weekListView;
    Button AddWeekButton;
    EditText InsertWeekEditText;
    String weekNumber;
    String subjectName;
    String subjectCode;
    User user;

    DatabaseReference mDatabase;
    DatabaseReference mRef;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_week_list);
        FirebaseApp.initializeApp(this);

        FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
        FirebaseUser firebaseUser = firebaseAuth.getCurrentUser();

        Intent moveToDetailIntent = this.getIntent();
        subjectName = moveToDetailIntent.getExtras().getString("Subject");
        subjectCode = moveToDetailIntent.getExtras().getString("Fagkode");

        mDatabase = FirebaseDatabase.getInstance().getReference().child("Studentfag").child(subjectCode).child("Week");
        mRef = FirebaseDatabase.getInstance().getReference().child("Users").child(firebaseUser.getUid()).child("User info");

        weekListView = (ListView) findViewById(R.id.WeekListView);
        AddWeekButton = (Button) findViewById(R.id.AddWeekButton);
        InsertWeekEditText = (EditText) findViewById(R.id.InsertWeek);

        String userID = firebaseUser.getUid();
        mRef.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                user = dataSnapshot.getValue(User.class);
                if (user.isStudent){
                    View a = weekListView;
                    a.setMinimumHeight(80);
                    View b = AddWeekButton;
                    b.setVisibility(View.GONE);
                    View c = InsertWeekEditText;
                    c.setVisibility(View.GONE);
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        adapter = new ArrayAdapter<String>(getBaseContext(), android.R.layout.simple_list_item_1, weekList);
        weekListView.setAdapter(adapter);
        weekListView.setOnItemClickListener(this);
        AddWeekButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                weekNumber= InsertWeekEditText.getText().toString();
                mDatabase.child(weekNumber).child("id").setValue(weekNumber);
            }
        });

        mDatabase.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                String week = dataSnapshot.getKey().toString();
                    weekList.add("Week: " + week);
                    adapter.notifyDataSetChanged();
                }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            //Urelevante metoder for oss.
            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {}
            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {}
            @Override
            public void onCancelled(DatabaseError databaseError) {}
        });

    }

The problem is that when I build a new activity in my setup method it complains because this sentence:

mRef = FirebaseDatabase.getInstance().getReference().child("Users").child(firebaseUser.getUid()).child("User info");

is not able to build, when we don't have a firebase user. Therefore I tried to Mock a firebaseuser in my testclass. The question is, how can I tell the class that it should use the mocked firebaseuser in onCreate? Is there a way to "send" the mocked object over? Thanks!

The beginning of my setup method:

  @Before
public void setUp() throws Exception {

    Intent i = new Intent();
    i.putExtra("Subject", "Matematikk 1");
    i.putExtra("Fagkode", "TMA4100");

    FirebaseUser mockFirebaseUser = mock(FirebaseUser.class);
    when(mockFirebaseUser.getUid()).thenReturn("uTZpVPPz8NT2LOvP4ufjs1L6r3P2");

    Activity activity = Robolectric.buildActivity(WeekListActivity.class).withIntent(i).create().get();

}

Answer 1

As usual, I suggest everybody to not mix presentation and storage code. And this is a question for another topic.

And here the trick how you can achieve what you want. First, extract method for Firebase initialisation and providing FirebaseAuth:

 @VisibleForTest
 @NonNull
 FirebaseAuth initAndReturnFirebaseAuth() {
     FirebaseApp.initializeApp(this);
     FirebaseAuth firebaseAuth = FirebaseAuth.getInstance();
 }

Second, create test activity and override this method:

public class TestWeekListActivity extends WeekListActivity {
    @Override
    @NonNull
    FirebaseAuth initAndReturnFirebaseAuth() {
       FirebaseAuth authMock = mock(FirebaseAuth.class);
       when(authMock.getCurrentUser()).thenReturn(mockFirebaseUser);
       return authMock;
    }
}

And then use test activity in test instead of you real activity.

Hope it helps!