使用注入对 NestJS 控制器进行单元测试

Question

我需要为使用 NestJS 注入的控制器进行单元测试。

我不知道如何模拟和监视此服务 (MyEmitter)。 我需要在 beforeEach() 内部的 test.controller.spec.ts 中声明它，但是如何声明呢？

test.controller.ts

import {
  Controller,
  Body,
  Post,
} from '@nestjs/common';
import {
  WebhookDto,
} from './dto/webhook.dto';
import { MyEmitter } from './test.events';
import { InjectEventEmitter } from 'nest-emitter';

@Controller()
export class TestController {
  constructor(
    @InjectEventEmitter() private readonly myEmitter: MyEmitter,
  ) {}

  @Post('webhook')
  public async postWebhook(
    @Body() webhookDto: WebhookDto,
  ): Promise<void> {
    ...
    this.myEmitter.emit('webhook', webhookDto);
  }
}

test.controller.spec.ts

import { Test, TestingModule } from '@nestjs/testing';
import { TestController } from './test.controller';
import EventEmitter = require('events');
import { EVENT_EMITTER_TOKEN } from 'nest-emitter';
import { MyEmitter } from './test.events';

describe('Test Controller', () => {
  let testController: TestController;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      imports: [],
      providers: [
        {
          provide: EVENT_EMITTER_TOKEN,
          useValue: {
            emit: jest.fn(),
          },
        },
      ],
      controllers: [TestController],
    }).compile();

    testController = module.get<TestController>(TetsController);
  });

  describe('postWebhook', () => {
    it('should send the event', async () => {
      const myEmitterSpy = jest.spyOn(myEmitter, 'emit');
      const result = await testController.postWebhook({...});
      expect(myEmitterSpy).toBeCalledTimes(1);
    });
  });
});

非常感谢您的帮助。

Answer 1

与其注入每个依赖项（应单独测试），不如使用 jest.spyOn 更好，因为控制器具有服务依赖项或可能具有其他依赖项的依赖项。

我们应该模拟将在当前测试中调用的方法。

这是示例控制器测试。

import { SampleController } from './sample.controller';
import { SampleService } from './sample.service';

describe('SampleController', () => {
  let sampleController: SampleController;
  let sampleService: SampleService;

  beforeEach(() => {
    // SampleService depends on a repository class
    // Passing null becasue SampleService will be mocked
    // So it does not need any dependencies.
    sampleService = new SampleService(null);
    // SampleController has one dependency SampleService
    sampleController = new SampleController(sampleService);
  });

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

  describe('findAll', () => {
    it('should return array of samples', async () => {
      // Response of findAllByQuery Method
      // findAllByQUeryParams is a method of SampleService class.
      // I want the method to return an array containing 'test' value'.
      const expectedResult = ['test'];

      // Creating the mock method
      // The method structure is the same as the actual method structure.
      const findAllByQueryParamsMock = async (query: any) => expectedResult;

      // I am telling jest to spy on the findAllByQueryParams method
      // and run the mock method when the findAllByQueryParams method is called in the controller.
      jest
        .spyOn(sampleService, 'findAllByQueryParams')
        .mockImplementation(findAllByQueryParamsMock);

      const actualResult = await sampleController.findAll({});

      expect(actualResult).toBe(expectedResult);
    });
  });
});

Answer 2

使用您当前的设置，最简单的方法是使用module.get()，就像您已经用于控制器一样，并传入EVENT_EMITTER_TOKEN 常量，然后将其保存到@987654324 中声明的值@block，就像let testController: TestController 的工作原理一样。这样的事情就足够了：

import { Test, TestingModule } from '@nestjs/testing';
import { TestController } from './test.controller';
import EventEmitter = require('events');
import { EVENT_EMITTER_TOKEN } from 'nest-emitter';
import { MyEmitter } from './test.events';

describe('Test Controller', () => {
  let testController: TestController;
  let myEmitter: MyEmitter;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      imports: [],
      providers: [
        {
          provide: EVENT_EMITTER_TOKEN,
          useValue: {
            emit: jest.fn(),
          },
        },
      ],
      controllers: [TestController],
    }).compile();

    testController = module.get<TestController>(TetsController);
    myEmitter = module.get<MyEmitter>(EVENT_EMITTER_TOKEN);
  });

  describe('postWebhook', () => {
    it('should send the event', async () => {
      const myEmitterSpy = jest.spyOn(myEmitter, 'emit'); // you can also add on mockResponse type functions here like mockReturnValue and mockResolvedValue
      const result = await testController.postWebhook({...});
      expect(myEmitterSpy).toBeCalledTimes(1);
    });
  });
});