nodejs中的Redis模拟不能存根不存在的属性createClient答案

【问题标题】：Redis mock in nodejs cannot stub non-existent property createClientnodejs中的Redis模拟不能存根不存在的属性createClient
【发布时间】：2020-11-04 15:23:18
【问题描述】：

我在尝试使用 mocha 和 sinon 在 NodeJS 中模拟 redis createClient() 方法时遇到问题。这是我的 index.js 的 sn-p。在socket类里面，有一个create redis连接。现在在我的单元测试中，我遇到了这个错误TypeError: Cannot stub non-existent property createClient。我似乎无法弄清楚为什么？是不是因为某种嘲弄的顺序？

const express = require("express");
const http = require('http');
const redis = require('redis');
const expressApp = express();
const server = http.createServer(expressApp);
const io = require('socket.io')(server, {
    pingInterval: 10000,
    pingTimeout: 5000
});
const config = require('config');
const log = require('gelf-pro');
const HTTP_PORT = 3000;

// Socket IO call backs
io.on("connection", (client) => {    
    new Socket(client);
});

// export the server so it can be easily called for testing
exports.server = server.listen(HTTP_PORT, () => {
    log.info('socketio server started at port ' + HTTP_PORT);
});

单元测试代码：

'use strict'

var expect = require('chai').expect
  , redis = require('redis')
  , redisMock = require('redis-mock')
  , sinon = require('sinon')
  , io = require('socket.io-client')
  , ioOptions = { 
      transports: ['websocket']
    , forceNew: true
    , reconnection: false
  }
  , testMsg = JSON.stringify({message: 'HelloWorld'})
  , sender
  , receiver
  



describe('Chat Events', function(){
  beforeEach(function(done){

    sinon
      .stub(redis.RedisClient.prototype, 'createClient')
      .callsFake(function() {
        console.log('mock redis called');
        return redisMock.createClient();
      });
    
    // connect two io clients
    sender = io('http://localhost:3000/', ioOptions)
    receiver = io('http://localhost:3000/', ioOptions)
    
    // finish beforeEach setup
    done()
  })
  afterEach(function(done){
    
    // disconnect io clients after each test
    sender.disconnect()
    receiver.disconnect()
    done()
  })

  describe('Message Events', function(){
    it('Clients should receive a message when the `message` event is emited.', function(done){
      sender.emit('message', testMsg)
      receiver.on('ackmessage', function(msg){
        expect(msg).to.contains(testMsg)
        done()
      })
    })
  })
})

【问题讨论】：

标签： javascript node.js unit-testing redis sinon

【解决方案1】：

redis.createClient 方法是一个独立的函数，不是原型的方法。如果你使用 TypeScript，我们可以检查 redis 包的类型。

index.d.ts:

export function createClient(port: number, host?: string, options?: ClientOpts): RedisClient;
export function createClient(unix_socket: string, options?: ClientOpts): RedisClient;
export function createClient(redis_url: string, options?: ClientOpts): RedisClient;
export function createClient(options?: ClientOpts): RedisClient;

所以，你应该这样存根：

index.js:

const redis = require('redis');

function main() {
  redis.createClient();
}

module.exports = main;

index.test.js:

const main = require('./');
const redis = require('redis');
const sinon = require('sinon');

describe('62909606', () => {
  it('should pass', () => {
    const createClientStub = sinon.stub(redis, 'createClient').callsFake(function() {
      console.log('mock redis called');
    });
    main();
    sinon.assert.calledOnce(createClientStub);
  });
});

带有覆盖率报告的单元测试结果：

  62909606
mock redis called
    ✓ should pass


  1 passing (9ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |     100 |      100 |     100 |     100 |                   
 index.js |     100 |      100 |     100 |     100 |                   
----------|---------|----------|---------|---------|-------------------

【讨论】：