Mock AngularFireAuth When Unit Testing an Angular Service

I have an authService which when instantiated subscribes to AngularFireAuth's Observable authState and sets the services' internal (private) property authState.

So I can unit test authService I highjack the services' internal authState with Reflect.get/set in my test specs so I can control its value.

The problem is of course authService is still subscribing to AngularFireAuth's Observable authState during its instantiation and I don't want, nor need it to.

I presume I need to mock out AngularFireAuth which fakes a subscription and doesn't actually communicate to Firebase? New to unit tests I am at a loss as to how I should do this.

auth.service.ts

import { Injectable } from '@angular/core';

import { AngularFireAuth } from 'angularfire2/auth';
import * as firebase from 'firebase/app';
import { Observable } from 'rxjs/Rx';

@Injectable()
export class AuthService {
  private authState: firebase.User;

  constructor(private afAuth: AngularFireAuth) { this.init(); }

  private init(): void {
    this.afAuth.authState.subscribe((authState) => {
      if (authState === null) {
        this.afAuth.auth.signInAnonymously()
          .then((authState) => {
            this.authState = authState;
          })
          .catch((error) => {
            throw new Error(error.message);
          });
      } else {
        this.authState = authState;
      }

      console.log(authState);
    }, (error) => {
      throw new Error(error.message);
    });
  }

  public get currentUid(): string {
    return this.authState ? this.authState.uid : undefined;
  }

  public get currentUser(): firebase.User {
    return this.authState ? this.authState : undefined;
  }

  public get currentUserObservable(): Observable<firebase.User> {
    return this.afAuth.authState;
  }

  public get isAnonymous(): boolean {
    return this.authState ? this.authState.isAnonymous : false;
  }

  public get isAuthenticated(): boolean {
    return !!this.authState;
  }

  public logout(): void {
    this.afAuth.auth.signOut();
  }
}

auth.service.spec.ts

import { async, fakeAsync, inject, TestBed, tick } from '@angular/core/testing';

import { AngularFireModule } from 'angularfire2';
import { AngularFireAuth, AngularFireAuthModule } from 'angularfire2/auth';
import * as firebase from 'firebase/app';
import 'rxjs/add/observable/of';
// import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { Observable } from 'rxjs/Rx';

import { AuthService } from './auth.service';
import { environment } from '../../environments/environment';

const authState = {
  isAnonymous: true,
  uid: '17WvU2Vj58SnTz8v7EqyYYb0WRc2'
} as firebase.User;

describe('AuthService', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [AngularFireModule.initializeApp(environment.firebaseAppConfig)],
      providers: [
        AngularFireAuth,
        AuthService
      ]
    });
  });

  it('should be defined', inject([ AuthService ], (service: AuthService) => {
    expect(service).toBeDefined();
  }));

  it('.currentUser should be anonymous', inject([ AuthService ], (service: AuthService) => {
    Reflect.set(service, 'authState', authState);

    expect(service.currentUser).toBe(authState);
  }));

  it('.currentUser should be undefined', inject([ AuthService ], (service: AuthService) => {
    expect(service.currentUser).toBe(undefined);
  }));

  it('.currentUserObservable should be anonymous', inject([ AuthService ], (service: AuthService) => {
    Reflect.set(service, 'authState', authState);

    service.currentUserObservable.subscribe((value) => {
      expect(value).toBe(authState);
    });
  }));

  it('.currentUserObservable should be undefined', inject([ AuthService ], (service: AuthService) => {
    service.currentUserObservable.subscribe((value) => {
      expect(value).toBe(undefined);
    });
  }));

  it('.currentUid should be of type String', inject([ AuthService ], (service: AuthService) => {
    Reflect.set(service, 'authState', authState);

    expect(service.currentUid).toBe(authState.uid);
  }));

  it('.currentUid should be undefined', inject([ AuthService ], (service: AuthService) => {
    expect(service.currentUid).toBe(undefined);
  }));

  it('.isAnonymous should be false', inject([ AuthService ], (service: AuthService) => {
    expect(service.isAnonymous).toBe(false);
  }));

  it('.isAnonymous should be true', inject([ AuthService ], (service: AuthService) => {
    Reflect.set(service, 'authState', authState);

    expect(service.isAnonymous).toBe(true);
  }));
});

For bonus points the two excluded tests (.currentUserObservable should be anonymous and .currentUserObservable should be undefined) throw the error Error: 'expect' was used when there was no current spec, this could be because an asynchronous test timed out but only when I log to the console during authService's instantiation. I'm wondering why this would be?