Spectron，mocha和chai可以声称变量在Electron-app中具有预期值吗？

Question

我们如何断言html中嵌入的javascript变量在使用电子构建的应用程序中具有一些预期价值？目前的测试框架是spectron，mocha，chai，chai.should（）和chai.use（chaiAsPromised）。

我想断言全局变量foo的值为'foo'。当我尝试foo.should.equal('foo')时，我得到了ReferenceError: foo is not defined at Context.<anonymous> (testspec.js:63:28)

下面是一个重新设计的spec.js.

const Application = require('spectron').Application
const assert = require('assert')
const electronPath = require('electron') // Require Electron from the binaries included in node_modules.
const path = require('path')
const chai = require('chai');
const chaiAsPromised = require('chai-as-promised');
const should = require('chai').should();

describe('Isolated testbeds house independent suites of tests.', function() {
  this.timeout(30000);

  before(function() {
    this.app = new Application({
      path: electronPath,

      // directory structure:

      //  |__ myProject
      //     |__ ...
      //     |__ main.js
      //     |__ package.json
      //     |__ index.html
      //     |__ ...
      //     |__ test
      //        |__ spec.js  <- You are here! ~ Well you should be.

      args: [path.join(__dirname, '..')]
    })
    return this.app.start()
  });

  after(function() {
    if (this.app && this.app.isRunning()) {
      return this.app.stop()
    }
  });

/* BELOW IS THE TEST IN QUESTION */
  it('should have a given value', function() {
    return Promise.resolve(foo).should.eventually.equal('foo'); // HERE IS THE LINE IN QUESTION
  });

})