How can I test observables in Angular using the CLI?

How can I test observables in Angular using the CLI?

You can test observables in Angular by using the TestBed and HttpClientTestingModule. Would you like a code example?

Yes, please provide a code example for testing an observable.

Sure! Here's a simple example:

import { TestBed } from '@angular/core/testing';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { MyService } from './my.service';

describe('MyService', () => {
  let service: MyService;
  let httpMock: HttpTestingController;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [HttpClientTestingModule],
      providers: [MyService]
    });
    service = TestBed.inject(MyService);
    httpMock = TestBed.inject(HttpTestingController);
  });

  it('should fetch data from observable', () => {
    service.getData().subscribe(data => {
      expect(data).toBeTruthy();
    });

    const req = httpMock.expectOne('api/data');
    expect(req.request.method).toBe('GET');
    req.flush({});
  });

  afterEach(() => {
    httpMock.verify();
  });
});

This tests an observable that fetches data from an API.

What are some common mistakes to avoid when testing observables?

Common mistakes include not unsubscribing from observables, not using the HttpTestingController properly, and forgetting to verify HTTP requests.