Angular2 - Testing a component with service dependency and external template

When I try to implement a test like this:

import { ComponentFixture, TestBed, async } from '@angular/core/testing';
import { RouterTestingModule } from '@angular/router/testing';
import { By }              from '@angular/platform-browser';
import { DebugElement }    from '@angular/core';
import { Observable } from 'rxjs/Observable';

import { SharedModule }        from '../shared/shared.module';
import { AuthInterface, AuthService, Credentials } from '../core/auth/index';
import { LoginComponent } from './login.component';

let comp: LoginComponent;
let fixture: ComponentFixture<LoginComponent>;
let de: DebugElement;
let el: HTMLElement;

////////  SPECS  /////////////

describe('Login component ', function() {

    const AuthServiceStub: AuthInterface = {
        isLoggedIn: true,
        redirectUrl: '/home',

        isAuthTokenStored(): boolean {
            return false;
        },

        isAuthTokenExpired(): boolean {
            return false;
        },

        login(input: Credentials): Observable<boolean> {
            return Observable.of(true);
        },

        logout(): void { }
    };

    beforeEach(async(() => {
        TestBed.configureTestingModule({
            imports: [
                RouterTestingModule,
                SharedModule
            ],
            declarations: [LoginComponent],
            providers: [{ provide: AuthService, useValue: AuthServiceStub }]
        }).compileComponents().then(() => {
            fixture = TestBed.createComponent(LoginComponent);
            comp = fixture.componentInstance;
        });
    }));

    describe('Basic test: ', function() {
        it('should instantiate a LoginComponent', async(() => {
            expect(comp instanceof LoginComponent).toBe(true, 'should create LoginComponent');
        }));
    });
});

The one and only test present it this test suite fails and I get the following error:

Error: No provider for AuthService!

The problem with this component is that it has an external HTML template, thus I have to use the async callback function in the beforeEach instruction in order to call the TestBed.compileComponents() method.

On the other side, this same test suite succeds if I use an inline template and I replace async with a regular anonymous function.