Angular 7单元测试错误：StaticInjectorError（DynamicTestModule）[PersonService-> HttpClient]

Question

我是Angular单元测试的新手。当我使用服务进行单元测试时，面临以下问题。

Error: StaticInjectorError(DynamicTestModule)[PersonService -> HttpClient]: 
StaticInjectorError(Platform: core)[PersonService -> HttpClient]: 
NullInjectorError: No provider for HttpClient!

import { TestBed, async, inject } from '@angular/core/testing';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { PersonService } from './person.service';

describe('PersonService', () => {
  let personService: PersonService;
  let httpMock: HttpTestingController;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        HttpClientTestingModule
      ],
      providers: [
        PersonService
      ],
    });

    personService = TestBed.get(PersonService);
    httpMock = TestBed.get(HttpTestingController);
  });

  it(`should fetch posts as an Observable`, async(inject([HttpTestingController, PersonService],
    (httpClient: HttpTestingController, personService: PersonService) => {

      const postItem = [
        {
          "userId": 1,
          "id": 1,
          "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
          "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
        },
        {
          "userId": 1,
          "id": 2,
          "title": "qui est esse",
          "body": "est rerum tempore vitae\nsequi sint nihil reprehenderit dolor beatae ea dolores neque\nfugiat blanditiis voluptate porro vel nihil molestiae ut reiciendis\nqui aperiam non debitis possimus qui neque nisi nulla"
        },
        {
          "userId": 1,
          "id": 3,
          "title": "ea molestias quasi exercitationem repellat qui ipsa sit aut",
          "body": "et iusto sed quo iure\nvoluptatem occaecati omnis eligendi aut ad\nvoluptatem doloribus vel accusantium quis pariatur\nmolestiae porro eius odio et labore et velit aut"
        }
      ];


      personService.getPosts()
        .subscribe((posts: any) => {
          expect(posts.length).toBe(3);
        });

      let req = httpMock.expectOne('https://myweb/posts');
      expect(req.request.method).toBe("GET");

      req.flush(postItem);
      httpMock.verify();

    })));
});