Angular2中的单元测试spyOn可观察服务

Angular 2中使用`spyOn`进行可观察服务的单元测试

typescript
// data.service.ts
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
@Injectable({
  providedIn: 'root'
})
export class DataService {
  constructor(private http: HttpClient) {}
  getData(): Observable {
    return this.http.get('https://api.example.com/data');
  }
}

typescript
// data.service.spec.ts
import { TestBed } from '@angular/core/testing';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { DataService } from './data.service';

typescript
// data.service.spec.ts
describe('DataService', () => {
  let service: DataService;
  let httpTestingController: HttpTestingController;
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [HttpClientTestingModule],
      providers: [DataService]
    });
    service = TestBed.inject(DataService);
    httpTestingController = TestBed.inject(HttpTestingController);
  });
  afterEach(() => {
    httpTestingController.verify();
  });
  it('should retrieve data from the API via GET', () => {
    const testData = { message: 'Hello, World!' };
    service.getData().subscribe(data => {
      expect(data).toEqual(testData);
    });
    const req = httpTestingController.expectOne('https://api.example.com/data');
    expect(req.request.method).toEqual('GET');
    req.flush(testData);
  });
});