Angular测试失败，并显示以下错误：“错误：超时-jasmine.DEFAULT_TIMEOUT_INTERVAL指定的超时内未调用异步回调”

Question

我将在Angular 7中使用业力（4.0.1）和茉莉（2.8.0）启动一些测试。问题是，在我的计算机中，测试总是失败，而另一个失败。错误是：错误：超时-在jasmine.DEFAULT_TIMEOUT_INTERVAL指定的超时内未调用异步回调。我在stackoverflow和其他地方进行了搜索，但是还行不通。

I have already modified some values in karma.conf.js like browserDisconnectTimeout, browserDisconnectTolerance, browserNoActivityTimeout but anything. 

import {async, TestBed} from '@angular/core/testing';
import {RouterTestingModule} from '@angular/router/testing';
import {AppComponent} from './app.component';
import {LayoutsModule} from './layouts/layouts.module';
import {HttpClientTestingModule} from '@angular/common/http/testing';
import {ToastrModule} from 'ngx-toastr';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule, LayoutsModule, HttpClientTestingModule, BrowserAnimationsModule, ToastrModule.forRoot()
      ],
      declarations: [
        AppComponent
      ],
    }).compileComponents();
  }));

  it('should create the app', () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.debugElement.componentInstance;
    expect(app).toBeTruthy();
  });

  it(`should have as title 'sfr-fr'`, () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.debugElement.componentInstance;
    expect(app.title).toEqual('sfr-fr');
  });

  it('should render a wrapper div', () => {
    const fixture = TestBed.createComponent(AppComponent);
    fixture.detectChanges();
    const compiled = fixture.debugElement.nativeElement;
    expect(compiled.querySelector('.wrapper')).toBeDefined();
  });
});