Unit Testing with Firebase

Question

I am building an android app which uses Firebase as the back-end and an model, view, presenter architecture. However, the fact that Firebase is a cloud service complicates the automated testing in my android app. So far I have built most of the authentication system, but am unable to see how to implement unit tests for the Firebase code in my app. In terms of end to end testing I am also stuck.

Since testing is fundamental to any android app and without it application developers can't be sure what they have implemented is functioning as expected, I can't really progress any further without automated tests.

In conclusion, my question is:

Generally, how do you implement Firebase automated testing in an android app?

EDIT:

As an example could someone unit test the following method?

public void addUser(final String name, final String birthday,
                        final String email, final String password) {
        Firebase mUsersNode = Constants.mRef.child("users");
        final Firebase mSingleUser = mUsersNode.child(name);
        mSingleUser.runTransaction(new Transaction.Handler() {
            @Override
            public Transaction.Result doTransaction(MutableData mutableData) {

                mSingleUser.child("birthday").setValue(birthday);
                mSingleUser.child("email").setValue(email);
                mSingleUser.child("password").setValue(password);
                return Transaction.success(mutableData);
            }

            @Override
            public void onComplete(FirebaseError firebaseError, boolean b, DataSnapshot dataSnapshot) {
                if(firebaseError != null) {
                        mSignUpPresenter.addUserFail(firebaseError);
                    } else {
                        mSignUpPresenter.addUserComplete();
                }
            }
        });
    }

Answer 1

UPDATE 2020: "So far this year (2020), this problem seems to have been solved using a (beta, at the date of this comment) Firebase emulator: Build unit tests using Fb Emulators and Unit testing security rules with the Firebase Emulator Suite, at YouTube This is done locally in the developer's computer. – carloswm85"

I found this https://www.firebase.com/blog/2015-04-24-end-to-end-testing-firebase-server.html but the article is over a year old. I only scanned it, I'll give it a more thorough read in a bit.

Either way, we really need the equivalent of the local Google AppEngine Backend that you can run in Intellij (Android Studio). Testing cannot be an afterthought in 2016. Really hoping one of the awesome Firebase devs notices this thread and comments. Testing should be part of their official guides.