如何模擬節點redis模塊的createClient方法

Question

我試圖通過在創建新客戶端時使用redis-mock模塊代替redis模塊來避免對正在運行的redis服務器的依賴。 到目前為止，我發現不可能模擬相關方法： createClient

我閱讀了有關存根的sinon文檔，並通過了一個示例 （在Googling上找到后找到），並基於這些示例進行了設置：

一個示例應用

// src/app.js

'use strict';

// import modules
const  express = require('express')
    , bluebird = require('bluebird')
    , redis    = require('redis')
;

// promisify redis
bluebird.promisifyAll(redis.RedisClient.prototype);
bluebird.promisifyAll(redis.Multi.prototype);

// define constants
const app    = express()
    , client = redis.createClient()
    , port   = 3000
;

// set some values
client
  .setAsync('12345', JSON.stringify({vacancyId:12345}))
  .catch(err => console.log(`[ERROR]: error setting value - ${err}`));

// define routes
app.get('/api/vacancy/:vacancyId', (req, res) => {
  client
    .getAsync(req.params.vacancyId)
    .then(val => res.send(val))
    .catch(err => console.log(`[ERROR]: error getting value - ${err}`))
});

// listen on port
app.listen(port);

// export the app
module.exports = app;

和相應的測試

// test/app.js

'use strict';

// import modules
const chai           = require('chai')
    , chaiAsPromised = require('chai-as-promised')
    , chaiHttp       = require('chai-http')
    , redis          = require('redis')
    , redisMock      = require('redis-mock')
    , sinon          = require('sinon')
    , app            = require('../src/app.js')
;

// configure chai
chai.use(chaiAsPromised);
chai.use(chaiHttp);

// define constants
const expect   = chai.expect
    , response = JSON.stringify({vacancyId:12345})
;

// now test
describe.only('App', function() {
  before(function() {
    sinon
      .stub(redis.RedisClient.prototype, 'createClient')
      .callsFake(function() {
        console.log('[TEST]: i never get here :(');
        return redisMock.createClient();
      });
  });

  describe('/api/vacancy/:vacancyId', function() {
    it('should return the expected response', function() {
      return expect(chai.request(app).get('/api/vacancy/12345'))
        .to.eventually
        .have.include({status:200})
        .and
        .nested.include({text:response});
    });
  });
});

我希望測試能夠通過（並且在刪除存根並指向運行中的Redis服務器時會通過）：

> scratch-node@1.0.0 test /Users/nonyiah/.src/scratch-node
> mocha --exit



  App
    /api/vacancy/:vacancyId
      ✓ should return the expected response


  1 passing (41ms)

但是我得到了以下錯誤：

> scratch-node@1.0.0 test /Users/nonyiah/.src/scratch-node
> mocha --exit



  App
    1) "before all" hook in "App"


  0 passing (10ms)
  1 failing

  1) App
       "before all" hook in "App":
     TypeError: Cannot stub non-existent own property createClient
      at Sandbox.stub (node_modules/sinon/lib/sinon/sandbox.js:308:19)
      at Context.<anonymous> (test/app.js:26:8)



npm ERR! Test failed.  See above for more details.

實現這種嘲笑的正確方法是什么？

Answer 1

原來，我是在加載應用程序后創建存根的。 我需要移動應用程序的實例化：

    // , app            = require('../src/app.js')

存根創建后到：

  describe('/api/vacancy/:vacancyId', function() {
    it('should return the expected response', function() {
      let app = require('../src/app.js');

      return expect(chai.request(app).get('/api/vacancy/12345'))
        .to.eventually
        .have.include({status:200})
        .and
        .nested.include({text:response});
    });
  });