[Angular & Unit Testing] Testing a RouterOutlet component

The way to test router componet needs a little bit setup, first we need to create a "router-stubs.ts". This file is a helper file.

// export for convenience.
export { ActivatedRoute, Router, RouterLink, RouterOutlet} from '@angular/router';

import { Component, Directive, Injectable, Input } from '@angular/core';
import { NavigationExtras } from '@angular/router';

@Directive({
  selector: '[routerLink]',
  host: {
    '(click)': 'onClick()'
  }
})
export class RouterLinkStubDirective {
  @Input('routerLink') linkParams: any;
  navigatedTo: any = null;

  onClick() {
    this.navigatedTo = this.linkParams;
  }
}

@Component({selector: 'router-outlet', template: ''})
export class RouterOutletStubComponent { }

@Injectable()
export class RouterStub {
  navigate(commands: any[], extras?: NavigationExtras) { }
}

// Only implements params and part of snapshot.paramMap
import { BehaviorSubject } from 'rxjs/BehaviorSubject';
import { convertToParamMap, ParamMap } from '@angular/router';

@Injectable()
export class ActivatedRouteStub {

  // ActivatedRoute.paramMap is Observable
  private subject = new BehaviorSubject(convertToParamMap(this.testParamMap));
  paramMap = this.subject.asObservable();

  // Test parameters
  private _testParamMap: ParamMap;
  get testParamMap() { return this._testParamMap; }
  set testParamMap(params: {}) {
    this._testParamMap = convertToParamMap(params);
    this.subject.next(this._testParamMap);
  }

  // ActivatedRoute.snapshot.paramMap
  get snapshot() {
    return { paramMap: this.testParamMap };
  }
}

/*
Copyright 2017 Google Inc. All Rights Reserved.
Use of this source code is governed by an MIT-style license that
can be found in the LICENSE file at http://angular.io/license
*/

The component we want to test:

<app-banner></app-banner>
<app-welcome></app-welcome>

<nav>
  <a routerLink="/dashboard">Dashboard</a>
  <a routerLink="/heroes">Heroes</a>
  <a routerLink="/about">About</a>
</nav>

<router-outlet></router-outlet>

import { Component } from '@angular/core';
@Component({
  selector: 'my-app',
  templateUrl: './app.component.html'
})
export class AppComponent { }

Testing setup:

beforeEach( async(() => {
  TestBed.configureTestingModule({
    declarations: [
      AppComponent,
      BannerComponent, WelcomeStubComponent,
      RouterLinkStubDirective, RouterOutletStubComponent
    ]
  })

  .compileComponents()
  .then(() => {
    fixture = TestBed.createComponent(AppComponent);
    comp    = fixture.componentInstance;
  });
}));

We need to declare 'RouterLinkStubDirective' & 'RouterOutletStubComponent' which we created in stub helper file.

beforeEach(() => {
  // trigger initial data binding
  fixture.detectChanges();

  // find DebugElements with an attached RouterLinkStubDirective
  linkDes = fixture.debugElement
    .queryAll(By.directive(RouterLinkStubDirective));

  // get the attached link directive instances using the DebugElement injectors
  links = linkDes
    .map(de => de.injector.get(RouterLinkStubDirective) as RouterLinkStubDirective);
});

Some tests:

it('can get RouterLinks from template', () => {
  expect(links.length).toBe(, 'should have 3 links');
  expect(links[].linkParams).toBe('/dashboard', '1st link should go to Dashboard');
  expect(links[].linkParams).toBe('/heroes', '1st link should go to Heroes');
});

it('can click Heroes link in template', () => {
  const heroesLinkDe = linkDes[];
  const heroesLink = links[];

  expect(heroesLink.navigatedTo).toBeNull('link should not have navigated yet');

  heroesLinkDe.triggerEventHandler('click', null);
  fixture.detectChanges();

  expect(heroesLink.navigatedTo).toBe('/heroes');
});