javascript - Node : How to assert if event callback function was called using sinon

Question

如何测试事件监听器的回调函数是否被调用？例如，我有以下代码，其中 app.js 通过 init.js Controller 初始化应用程序。

main.js 文件有一个类扩展和事件发射器，使对象成为事件发射器。

app.js

const initController = require('./init');
async function init() {
    initController.startMain();
}
init();

main.js

const events = require('events'),
ui = require('./ui');

module.exports.getMain = function () {
  class Main extends events.EventEmitter {
    constructor() {
      super();
      this.status = null;
    }
  }
  return new Main();
};

module.exports.init = () => {
  const main = this.getMain();
  ui.init(main);
  this.start(main);
}

module.exports.start = (main) => {
  ui.start(main);
  main.emit('http-init');
  main.emit('http-success');
  main.emit('http-error');
};

ui.js

function init(main) {
    main.on('http-init', onHttpInit.bind(this));
    main.on('http-success', onHttpSuccess.bind(this));
    main.on('http-error', onHttpError.bind(this));
    main.once('app-ready', onAppReady.bind(this));
  };

  function start (main) {};

  function onAppReady() {
    console.log('APP READY');
  };

  function onHttpInit() {
    console.log('HTTP INIT SEQUENCE');
  };

  function onHttpError(error) {
    console.log('HTTP ERROR SEQUENCE');
  };

  function onHttpSuccess() {
      console.log('HTTP SUCCESS SEQUENCE');
  };

  module.exports = exports = {
    init,
    start,
    onHttpInit,
    onHttpError,
    onHttpSuccess,
  };

init.js

exports.startMain = () => {

    console.log('Start application');

    // Load application modules
    const main = require('./main');

    // Start the application
    main.init();
 };

因此，当我运行命令 node app.js 时，我看到了以下输出

开始申请HTTP 初始化序列HTTP 成功序列HTTP 错误序列

这意味着监听器处于事件状态并且调用了函数。

ui.tests.js

const sinon = require('sinon'),
    main = require('../main').getMain(),
    proxyquire = require('proxyquire').noPreserveCache().noCallThru();

describe('UI Tests', () => {
    const sandbox = sinon.createSandbox();
    let controller = null;
    before(() => {
        controller = proxyquire('../ui', {});
    })
    describe('Testing Eventlisteners', ()=> {
        afterEach(() => {
            main.removeAllListeners();
        });
        const eventMap = new Map([
        [ 'http-init', 'onHttpInit' ],
        [ 'http-success', 'onHttpSuccess' ],
        [ 'http-error', 'onHttpError']
        ]);
        eventMap.forEach((value, key) => {
            it(`should register an eventlistener on '${key}' to ${value}`, () => {
                const stub = sinon.stub(controller, value);
                controller.init(main);
                main.emit(key);
                sinon.assert.called(stub);
            })
        })
    })
})    

然而，当我运行上面的测试时，即使我得到了输出，即调用了函数，但是，sinon assert 总是失败，说下面的内容:

  UI Tests
    Testing Eventlisteners
HTTP INIT SEQUENCE
      1) should register an eventlistener on 'http-init' to onHttpInit
HTTP SUCCESS SEQUENCE
      2) should register an eventlistener on 'http-success' to onHttpSuccess
HTTP ERROR SEQUENCE
      3) should register an eventlistener on 'http-error' to onHttpError


  0 passing (16ms)
  3 failing

 1) UI Tests
       Testing Eventlisteners
         should register an eventlistener on 'http-init' to onHttpInit:
     AssertError: expected onHttpInit to have been called at least once but was never called
      at Object.fail (node_modules/sinon/lib/sinon/assert.js:106:21)
      at failAssertion (node_modules/sinon/lib/sinon/assert.js:65:16)
      at Object.assert.(anonymous function) [as called] (node_modules/sinon/lib/sinon/assert.js:91:13)
      at Context.it (test/ui.tests.js:25:30)
  2) UI Tests
       Testing Eventlisteners
         should register an eventlistener on 'http-success' to onHttpSuccess:
     AssertError: expected onHttpSuccess to have been called at least once but was never called
      at Object.fail (node_modules/sinon/lib/sinon/assert.js:106:21)
      at failAssertion (node_modules/sinon/lib/sinon/assert.js:65:16)
      at Object.assert.(anonymous function) [as called] (node_modules/sinon/lib/sinon/assert.js:91:13)
      at Context.it (test/ui.tests.js:25:30)

  3) UI Tests
       Testing Eventlisteners
         should register an eventlistener on 'http-error' to onHttpError:
     AssertError: expected onHttpError to have been called at least once but was never called
      at Object.fail (node_modules/sinon/lib/sinon/assert.js:106:21)
      at failAssertion (node_modules/sinon/lib/sinon/assert.js:65:16)
      at Object.assert.(anonymous function) [as called] (node_modules/sinon/lib/sinon/assert.js:91:13)
      at Context.it (test/ui.tests.js:25:30)

我不知道为什么即使该函数至少被调用一次，测试也会失败，这可以从输出 HTTP INIT SEQUENCE、HTTP SUCCESS SEQUENCE 和 HTTP 错误序列 当我运行测试时。

我试着做 stub.should.have.been.called;。有了这个测试通过，但是，它并没有真正通过 stub.should.have.been.called; 或 stub.should.not.have.been.called; 不管怎样都通过测试，而不是后者未通过测试。

有人知道这个测试失败的原因吗？感谢您的帮助。

Answer 1

您运行 const stub = sinon.stub(controller, value); 来 stub 由您的 ui 模块导出的值。这确实改变了模块导出的值，但问题出在 ui 模块中的这段代码:

function init(main) {
    main.on('http-init', onHttpInit.bind(this));
    main.on('http-success', onHttpSuccess.bind(this));
    main.on('http-error', onHttpError.bind(this));
    main.once('app-ready', onAppReady.bind(this));
}

从这段代码的 Angular 来看，module.exports 是被你的调用sinon.stub(controller, value)改变了，但是这不会更改上面代码中符号 onHttpInit、onHttpSuccess 等符号的值，因为这些符号是 ui 范围内的局部符号模块。您可以随心所欲地改变 module.exports:它仍然对上面的代码没有影响。

您可以将代码更改为:

function init(main) {
    main.on('http-init', exports.onHttpInit.bind(this));
    main.on('http-success', exports.onHttpSuccess.bind(this));
    main.on('http-error', exports.onHttpError.bind(this));
    main.once('app-ready', exports.onAppReady.bind(this));
}

您可以直接使用 exports，因为您为 module.exports 和 exports 分配了相同的值，其中 module.exports =导出 = ...

此更改应该可以解决您遇到的直接问题。但是，我会在这里修改测试方法。您的测试标题为 should register an eventlistener on '${key}' to ${value} 但实际上您正在测试的不仅仅是事件监听器已注册，而且事件传播有效。实际上，您正在测试 EventEmitter 负责提供的功能。我将更改测试以对 main 对象的 on 方法进行 stub ，并验证是否已使用适当的值调用它。然后测试将测试它实际宣传的内容。