如何使用 Jest 和 Node.JS 测试由 Promise 返回的 RedisClient

Question

// client.js
const getCacheClient = async (configuration) => {
  return new Promise((resolve, reject) => {
    const redisClient = redis.createClient(configuration.port, configuration.host);
    // note that promise is fullfiled or rejected based on redis client events
    redisClient.on('ready', () => resolve(redisClient));
    redisClient.on('error', (redisError) => {
      console.log('Error connecting Redis', redisError.message);
      redisClient.quitAsync();
      return reject(redisError);
    });
  });
};

测试由 promise 返回但解析或拒绝基于事件处理程序的 Redis 客户端的正确方法是什么？

由于解决或拒绝是基于“成功/错误”事件，我不确定如何重新创建事件。我得到一个 '在 jest.setTimeout.Timeout 指定的 10000 毫秒超时内未调用异步回调 - 在 jest.setTimeout.Error 指定的 10000 毫秒超时内未调用异步回调：'

// client.test.js

import client, { __RewireAPI__ as API } from '../client';

describe('get-cache-client', () => {
  const mockBlueprint = { promisifyAll: jest.fn((x) => x) };
  const mockRedisClient = {
    getAsync: jest.fn(),
    setexAsync: jest.fn(),
    on: jest.fn(),
  };
  const mockRedis = {
    createClient: {
      on: jest.fn(),
    },
  };

  beforeEach(() => {
    API.__Rewire__('redis', mockRedis);
    API.__Rewire__('blueprint', mockBlueprint);
  });

  afterEach(() => {
    __rewire_reset_all__();
    mockRedis.createClient.mockReset();
  });

  describe('getCacheClient', () => {
    it('should create a client with the expected parameters', async (done) => {
      const config = {
        host: 'testrediscachehost',
        port: 1234,
        key: 'testrediscachekey',
      };
      mockRedis.createClient.on.mockReturnValue(mockRedisClient);
      const client = await expect(getCacheClient(config));
      // it gets stuck here, promise is never fulfilled or rejected
      // .... tests...
    });
  });
});

Answer 1

我没有看到任何使用 __Rewire__ 东西的理由。

使用jest.spyOn() 和jest.restoreAllMocks() 就足够了。

例如

client.js:

import redis from 'redis';

export const getCacheClient = async (configuration) => {
  return new Promise((resolve, reject) => {
    const redisClient = redis.createClient(configuration.port, configuration.host);
    redisClient.on('ready', () => resolve(redisClient));
    redisClient.on('error', (redisError) => {
      console.log('Error connecting Redis', redisError.message);
      redisClient.quit();
      return reject(redisError);
    });
  });
};

client.test.js:

import { getCacheClient } from './client';
import redis from 'redis';

describe('68492493', () => {
  afterEach(() => {
    jest.restoreAllMocks();
  });
  test('should create redis client and be ready', async () => {
    const config = {
      host: 'testrediscachehost',
      port: 1234,
      key: 'testrediscachekey',
    };
    const mRedisClient = {
      on: jest.fn().mockImplementation(function (event, handler) {
        if (event === 'ready') {
          handler();
        }
        return this;
      }),
      quit: jest.fn(),
    };
    const createClientSpy = jest.spyOn(redis, 'createClient').mockReturnValueOnce(mRedisClient);
    await getCacheClient(config);
    expect(createClientSpy).toBeCalledWith(1234, 'testrediscachehost');
    expect(mRedisClient.on).toBeCalledWith('ready', expect.any(Function));
  });

  test('should handle error', async () => {
    // Try test by yourself
  });
});

测试结果：

 PASS  examples/68492493/client.test.ts (8.739 s)
  68492493
    ✓ should create redis client and be ready (4 ms)

-----------|---------|----------|---------|---------|-------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-----------|---------|----------|---------|---------|-------------------
All files  |      75 |      100 |      80 |   66.67 |                   
 client.ts |      75 |      100 |      80 |   66.67 | 8-10              
-----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        9.548 s, estimated 10 s
Ran all test suites related to changed files.