Angular 4 unit testing with jasmine /karma with http post mocking - how to fix

Question

I have a service I want to unit test in angular 4 typescript jasmine.

Now, the http is doing a post , and it returns an identity, however

Answer 1

In order to achieve what you want, the mock you need is a simple function that returns the same as the POST would do normally; another thing is your test should not hit the server for real, so you would need something like this (you might need to add other dependencies):

import { HttpModule } from '@angular/http';
import { TrackerFormService } from './tracker-form.service'
import { Observable } from 'rxjs/Observable'

describe('TrackerFormService', () => {
// Mock the service like this and add all the functions you have in this fashion
let trackerFormService: TrackerFormService,
  mockService = {
    addSession: jasmine.createSpy('addSession').and.returnValue(Observable.of('your session object mock goes here'))
  };

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [HttpModule],
      providers: [{
        provide: TrackerFormService,
        useValue: mockService
      }]
    });
  });

  // Do this trick to inject the service every time, and just use `service` in your tests
  beforeEach(inject([TrackerFormService], (trackerFormService) => {
    service = trackerFormService;
  }));

  describe('addSession', () => {
    it('add session ', () => {
      let fakeResponse = null;

      // Call the service function and subscribe to it to catch the fake response coming from the mock.
      service.addSession().subscribe((value) => {
        // in here value will be whatever you put as returnValue (remember to keep the observable.of())
        fakeResponse = value;
      });

      // expects as in any test.
      expect(fakeResponse).toBeDefined();
      expect(fakeResponse).toBe('your session object mock goes here');
    });
  });
});