Angular Tests failed with : "Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL "

I'm launching some tests in Angular 7, with karma (4.0.1) and jasmine (2.8.0). The problem is that tests always failed in my computer wheras in another no. The error is : Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL. I made lof of searches in stackoverflow and elsewhere but it doesn't work yet.

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();
  });
});