Node.js 为什么回调连接到一个调用两次的事件？

我正在梳理教程，我很好奇为什么回调被调用多次——在本例中是两次。这是我的密码：

'use strict';

var chai = require('chai'),
    expect = chai.expect,
    sinon = require('sinon'),
    sinonChai = require('sinon-chai');

var Backbone = require('backbone'),
    _ = require('lodash/dist/lodash.underscore');

chai.use(sinonChai);

describe('Backbone.Events', function() {
  var myObj;

  beforeEach(function() {
    myObj = {};
    _.extend(myObj, Backbone.Events);
  });

  it('allows us to bind and trigger custom named events on an object', function() {
    var callback = sinon.spy();

    myObj.bind('custom event', callback);
    myObj.trigger('custom event');

    expect(callback).to.have.been.called;      // => passes
    expect(callback).to.have.been.calledOnce;  // => fails??
    expect(callback).to.have.been.calledTwice; // => passes, why?
  });
});

---

有什么见解吗？

您正在绑定和触发两个事件

自定义事件
自定义事件
和
事件

尝试将其更改为
custom\u事件