Lazy loading testing

app-routing.module.spec.ts

import { async, ComponentFixture, TestBed, fakeAsync, tick } from '@angular/core/testing';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { Router, RouterModule } from '@angular/router';
import { NgModuleFactoryLoader, Component, NgModule } from '@angular/core';
import { RouterTestingModule } from '@angular/router/testing';
import { routes } from './app-routing.module'
import { Location } from '@angular/common';

describe('PageNotfoundComponent', () => {
  let component: AppComponent;
  let fixture: ComponentFixture<AppComponent>;
  let router: Router;
  let location: Location;

  beforeEach(() => {
    fixture = TestBed.createComponent(AppComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
    router = TestBed.get(Router);
  });

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ AppComponent ],
      imports: [
        RouterTestingModule.withRoutes(routes),
        BrowserAnimationsModule,
        PageNotfoundModule,
        LoginModule
      ]
    }).compileComponents();
  }));

  @Component({ 
    template: '' 
  })
  class LazyLoadedComponent { }

  @NgModule({ 
    declarations: [LazyLoadedComponent] 
  })
  class LazyModule { }

  it('should navigate to 404 child path', fakeAsync(() => {
    router = TestBed.get(Router);
    router.initialNavigation();

    // Used to load ng module factories.
    const loader = TestBed.get(NgModuleFactoryLoader);
    location = TestBed.get(Location);

    // sets up stubbedModules
    loader.stubbedModules = {
      './page-notfound/page-notfound.module#PageNotfoundModule': LazyModule,
    };

    router.resetConfig([
      { path: '404', loadChildren: './page-notfound/page-notfound.module#PageNotfoundModule' },
    ]);

    router.navigateByUrl('/404');

    tick();

    fixture.detectChanges();

    expect(location.path()).toBe('/404');
  }));
});