javascript - 用 Jest 测试 NestJs 服务

Question

我正在寻找一种方法来使用 Jest 测试我的 NestJs PlayerController。我的 Controller 和服务声明:

import { QueryBus, CommandBus, EventBus } from '@nestjs/cqrs';

/**
 * The service assigned to query the database by means of commands
 */
@Injectable()
export class PlayerService {
    /**
     * Ctor
     * @param queryBus
     */
    constructor(
        private readonly queryBus: QueryBus,
        private readonly commandBus: CommandBus,
        private readonly eventBus: EventBus
    ) { }


@Controller('player')
@ApiUseTags('player')
export class PlayerController {
    /**
     * Ctor
     * @param playerService
     */
    constructor(private readonly playerService: PlayerService) { }

我的测试:

describe('Player Controller', () => {
  let controller: PlayerController;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      imports: [PlayerService, CqrsModule],
      controllers: [PlayerController],
      providers: [
        PlayerService,
      ],
    }).compile();


    controller = module.get<PlayerController>(PlayerController);
  });

  it('should be defined', () => {
    expect(controller).toBeDefined();
  });
...

Nest can't resolve dependencies of the PlayerService (?, CommandBus, EventBus). Please make sure that the argument at index [0] is available in the PlayerService context.

  at Injector.lookupComponentInExports (../node_modules/@nestjs/core/injector/injector.js:180:19)

有什么方法可以解决这个依赖问题？

Answer 1

它不起作用，因为您正在导入 PlayerService。您只能导入模块，提供者可以通过模块导入或在 providers 数组中声明:

imports: [PlayerService, CqrsModule]
          ^^^^^^^^^^^^^

---

但是，在单元测试中，您希望单独测试单个单元，而不是不同单元及其依赖项之间的交互。为 PlayerService 或 CqrsModule 的提供者提供模拟比导入或声明您的依赖项更好。

参见 this answer区分单元测试和端到端测试。

参见 this answer关于如何创建模拟。