Javascript 单元测试不受事件发射器约束的事件

我有下面的代码

  private client: any;

  this.client = mqtt.connect(url, mqttOptions);

  this.client.on('message', (topic: string, message: string) => {
   console.log('came inside onMessage');
    let ksiotMessage: KSIOTMessage;
    let receivedTopic: KSIOTTopic;
    receivedTopic = getValue(topic);
    ksiotMessage = {
      ksiotTopic: receivedTopic,
      payload: message
    };
    messageReceivedCallBack.onMessageReceived(ksiotMessage);
  });

在这里，当mqtt客户机发出消息事件时，将触发一个匿名函数。我无法控制它，也就是说不是我将它绑定到事件发射器。此外，我无法添加计时器并等待此事件触发，因为我已经使用sinon模拟了客户端的连接。所以没有真正的联系。那么，如何手动发出此消息事件并查看是否调用了messageReceivedCallBack的onMessageReceived？我不熟悉Javascript中的单元测试。目前，我正在使用mocha和sinon来满足我的单元测试需求

---

请给出建议。

首先，我不知道TypeScript，也不知道您的应用程序的内部结构，因此以下内容可能无法直接使用。但是，它可能会为您提供一些关于如何实现这些类型测试的想法

我提取了您的客户机代码（需要测试的代码）：

在您的代码中，不清楚

messageReceivedCallBack

来自何处。因为您必须能够从Sinon访问它，所以它应该位于可导入模块中（但是，这确实取决于导入是缓存的，就像

require（）

，我不确定TS是否会这样做）

下面是我使用的一个简单的模拟：

// callbacks.js
module.exports = {
  onMessageReceived(message) {}
};

最后，测试本身。它相当复杂，因为它需要做各种事情：

• 创建一个

  EventEmitter

  子类，用于将原始

  MqttClient

  替换为
• 各种函数和回调的存根
• 设置测试环境

守则：

// test.js
const mqtt = require('mqtt');

// The modules mentioned above.
const mqttModule              = require('./mqtt-module');
const messageReceivedCallBack = require('./callbacks');

// Set up Sinon and Chai
const sinon = require('sinon');
const chai  = require('chai');
let expect  = chai.expect;
chai.use(require('sinon-chai'));

// Create a fake client for testing purposes.
const EventEmitter = require('events').EventEmitter;
class Client extends EventEmitter {}

// The test case.
describe('my test case', () => {
  var mockClient;

  beforeEach(() => {
    mockClient = new Client();
    // mqtt.connect() returns a fake client instance, with
    // just enough logic to allow events to be emitted and
    // received.
    sinon.stub(mqtt, 'connect').returns(mockClient);

    // Call the setup of our MQTT class (this will likely be
    // entirely different in your case, but the idea is that
    // it gets called _after_ `mqtt.connect()` gets stubbed.
    mqttModule.setup();
  });

  afterEach(() => {
    // Restore the original.
    mqtt.connect.restore();
  });

  it('should call messageReceivedCallBack.onMessageReceived', () => {
    // The message that we're going to pass.
    let message = 'this is a test message';

    // We want to stub messageReceivedCallBack.onMessageReceived()
    sinon.stub(messageReceivedCallBack, 'onMessageReceived');

    // Emit a `message` event on our mock client, which will trigger
    // the `client.on('message', ...)` in your MQTT class.
    mockClient.emit('message', 'topic', message);

    // Test if the stub was called with the proper argument.
    expect(messageReceivedCallBack.onMessageReceived).to.be.calledWith(message);

    // Restore to the original function.
    messageReceivedCallBack.onMessageReceived.restore();
  });

});

---

大免责声明：我不知道TypeScript，也不知道应用程序的内部结构，所以下面的内容可能无法开箱即用。但是，它可能会为您提供一些关于如何实现这些类型测试的想法

我提取了您的客户机代码（需要测试的代码）：

在您的代码中，不清楚

messageReceivedCallBack

来自何处。因为您必须能够从Sinon访问它，所以它应该位于可导入模块中（但是，这确实取决于导入是缓存的，就像

require（）

，我不确定TS是否会这样做）

下面是我使用的一个简单的模拟：

// callbacks.js
module.exports = {
  onMessageReceived(message) {}
};

最后，测试本身。它相当复杂，因为它需要做各种事情：

• 创建一个

  EventEmitter

  子类，用于将原始

  MqttClient

  替换为
• 各种函数和回调的存根
• 设置测试环境

守则：

// test.js
const mqtt = require('mqtt');

// The modules mentioned above.
const mqttModule              = require('./mqtt-module');
const messageReceivedCallBack = require('./callbacks');

// Set up Sinon and Chai
const sinon = require('sinon');
const chai  = require('chai');
let expect  = chai.expect;
chai.use(require('sinon-chai'));

// Create a fake client for testing purposes.
const EventEmitter = require('events').EventEmitter;
class Client extends EventEmitter {}

// The test case.
describe('my test case', () => {
  var mockClient;

  beforeEach(() => {
    mockClient = new Client();
    // mqtt.connect() returns a fake client instance, with
    // just enough logic to allow events to be emitted and
    // received.
    sinon.stub(mqtt, 'connect').returns(mockClient);

    // Call the setup of our MQTT class (this will likely be
    // entirely different in your case, but the idea is that
    // it gets called _after_ `mqtt.connect()` gets stubbed.
    mqttModule.setup();
  });

  afterEach(() => {
    // Restore the original.
    mqtt.connect.restore();
  });

  it('should call messageReceivedCallBack.onMessageReceived', () => {
    // The message that we're going to pass.
    let message = 'this is a test message';

    // We want to stub messageReceivedCallBack.onMessageReceived()
    sinon.stub(messageReceivedCallBack, 'onMessageReceived');

    // Emit a `message` event on our mock client, which will trigger
    // the `client.on('message', ...)` in your MQTT class.
    mockClient.emit('message', 'topic', message);

    // Test if the stub was called with the proper argument.
    expect(messageReceivedCallBack.onMessageReceived).to.be.calledWith(message);

    // Restore to the original function.
    messageReceivedCallBack.onMessageReceived.restore();
  });

});

---

您的测试代码需要访问

this.client

和

messageReceivedCallBack

。是这样吗？this.client从“mqtt.connect”行分配了一个值。因此，我将退还我自己的存根。我需要知道如何触发此连接事件，以便测试内部代码。由于我已经中断了connect方法，“message”事件不会自动触发。我需要手动启动它。我不知道如何：（您的测试代码需要访问

this.client

和

messageReceivedCallBack

。是这样吗？this.client从“mqtt.connect”行分配了一个值。因此，我将返回我自己的存根。我需要知道如何启动此连接事件，以便测试内部代码。由于我已中断了连接方法，“消息”事件将不会自动启动。我需要手动启动它。我不知道如何：（非常棒的解决方案伙伴！：）非常棒的解决方案伙伴！：）