Angular Unit Test Cheats

0 - INDEX

1) Cleanly providing stubs in a test
2) Unit testing an interceptor
3) Mocking injection token

1 - dependent.service.spec.ts

/*************************************/
/**CLEANLY PROVIDING STUBS IN A TEST**/
/*************************************/

import {TestBed, inject, async} from '@angular/core/testing';

import { DependentService } from './dependent.service';
import {MasterService} from '../dataService/master.service';

describe('DependentService', () => {
  let masterStub;

  beforeEach(() => {
    masterStub = jasmine.createSpyObj('master', ['action']);
    TestBed.configureTestingModule({
      providers: [
        DependentService,
        {provide: MasterService, useValue: masterStub}
      ]
    });
  });

  it('checks dependent call', inject([DependentService, MasterService], (service: SearchHelperService, master: MasterService) => {
    // call function which calls masterService's function
    service.callMasterAction();
    
    expect(master.action as jasmine.Spy).toHaveBeenCalled();
  }));

2 - my.interceptor.spec.ts

/*******************************/
/**UNIT TESTING AN INTERCEPTOR**/
/*******************************/

import {TestBed, inject, async} from '@angular/core/testing';
import {HttpClientTestingModule, HttpTestingController} from '@angular/common/http/testing';
import {HTTP_INTERCEPTORS, HttpClient} from '@angular/common/http';

import {Observable} from 'rxjs/Observable';

import {MyInterceptor} from './myInterceptor.interceptor';

describe('MyInterceptor', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        HttpClientTestingModule
      ],
      providers: [
        {
          provide: HTTP_INTERCEPTORS,
          useClass: MyInterceptor,
          multi: true
        },
        HttpClient
      ]
    });
  });

  it('intercepts HTTP GET request',
    async(inject([HttpClient, HttpTestingController],
      (http: HttpClient, httpMock: HttpTestingController) => {
        // random mock data
        const url = '/mock';
        const data = [{id: 5}];

        // http get
        http.get(url).subscribe((response) => {
          // check side effects of your interceptor.
          // For instance, that response is not changed
          expect(response).toEqual(data);
        });

        const req = httpMock.expectOne((request) => request.url === url && request.method === 'GET');
        req.flush(data);

        // expect your interceptor's behaviour here. You could use spies and stubs for example
      })));

injection-token-mock.spec.ts

/***************************************/
/**MOCKING INJECTION TOKEN : APP_TOKEN**/
/***************************************/

import {TestBed, inject, async} from '@angular/core/testing';
import {APP_TOKEN, AppToken} from '../../../core/config/appToken';

describe('Injection Token Mock', () => {
  let appTokenStub;
  
  beforeEach(() => {
    appConfigStub = {
      endpoint: 'http://example.com'
    };
    TestBed.configureTestingModule({
      imports: [
        HttpModule
      ],
      providers: [
        Http,
        {provide: APP_TOKEN, useValue: appTokenStub}
      ]
    });
  });

  it('checks value of app_token', inject([APP_TOKEN], (token: AppToken) => {
    expect(token).toEqual(appConfigStub);
  }));