Angular firebase - Unit testing a service using angularFireAuth

Question

I have a core service that gets an instance of the firebase.auth obj and returns it with a getter. It is simple and looks as follows:

export class AuthService {

  ...
  constructor(private afAuth: AngularFireAuth,
              private afs: AngularFirestore) {
  ...
}

  public getAuthInstance(): FirebaseAuth {
    return this.afAuth.auth;
  }
}

Now I have a LoginService that needs the AuthService for logging into my app.

export class LoginService {

  constructor(private authService: AuthService) {
  }

  public login(email, password): Promise<UserCredential | string> {
    return this.authService.getAuthInstance().signInWithEmailAndPassword(email, password)
      .catch(() => Promise.reject('Login failed.'));
  }

Also not too complex. But now I want to test my login comp. - specifically the login method. I am not able to mock signInWithEmailAndPassword. I tried basically everything:

• jasmine.spies
• self created fake obj.

The test class looks as follows:

  ...
  const authStub: AuthService = jasmine.createSpyObj('AuthService', ['getAuthInstance']);
  const fireStub = {
    auth: {
      signInWithEmailAndPassword() {
        return Promise.resolve();
      }
    }
  };

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        {provide: AuthService, useValue: authStub},
        {provide: AngularFireAuth, useValue: fireStub},
        LoginService
      ]
    });
  });

  const spy = it('should call signInWithPasswordAndEmail', inject([LoginService], (service: LoginService) => {
    (<jasmine.Spy>authStub.getAuthInstance).and.returnValue({username: 'test'});
    spyOn(fireStub.auth, 'signInWithEmailAndPassword').and.callThrough();


    service.login(email, password).then(() => expect(spy).toHaveBeenCalledTimes(1));
  }));

Can anyone help me to get this damn test green? xD^^ The Error msg. That ist thrown is: this.getAuthInstance().signInWithEmail.... Is Not a function

Answer 1

After some Trial and Error I mocked the AuthService indirectly with AngularFireAuth and AngularFireStore the test configuration looks as follows:

describe('LoginService', () => {

  const email: string = 'email';
  const password: string = 'password';

  const authStub: any = {
    authState: {},
    auth: {
      signInWithEmailAndPassword() {
        return Promise.resolve();
      }
    }
  };

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [
        {provide: AngularFireAuth, useValue: authStub},
        {provide: AngularFirestore},
        LoginService
      ]
    });
    authStub.authState = of(null);
  });

  it('should call signInWithPasswordAndEmail', inject([LoginService], (service: LoginService) => {
    const mock = TestBed.get(AngularFireAuth);
    const spy = spyOn(authStub.auth, 'signInWithEmailAndPassword').and.callThrough();
    mock.auth = authStub.auth;

    service.login(email, password);

    expect(spy).toHaveBeenCalledWith(email, password);
  }));
});

It gets the job done. If someone has a better solution, I would be pleased to know.