问如何在使用Karma时访问规范文件中的Puppeteer对象？

EN

gulp.task('ui-test', (done) =>
  new karmaServer({
      configFile: __dirname + '/karma.conf.js',
      singleRun: true
  }, done).start()
)

process.env.CHROME_BIN = require('puppeteer').executablePath()

module.exports = function(config) {
  config.set({
    browsers: ['ChromeHeadless'],
    files: [
      {pattern: 'ui-testing/*.spec.js', included: false},
    ],
    // frameworks to use
    frameworks: ['mocha', 'chai'],
  })
}

puppeteer = require('puppeteer')    

describe('login test', function () {
  let page;

  before (async function () {
    const browser = await puppeteer.launch();
    page = await browser.newPage();
    await page.goto('http://google.com');
  });

  after (async function () {
    await page.close();
  })

  it('should load the google page', async function () {
    expect(await page.title()).to.eql('Google');
  });
});

06 07 2018 08:15:16.164:INFO [HeadlessChrome 0.0.0 (Mac OS X 10.13.5)]: Connected on socket F1USmhKrpR4Eau9aAAAA with id 26089338
HeadlessChrome 0.0.0 (Mac OS X 10.13.5) ERROR
  {
    "message": "Uncaught ReferenceError: require is not defined\nat ui-testing/login.spec.js:1:1\n\nReferenceError: require is not defined\n    at ui-testing/login.spec.js:1:1",
    "str": "Uncaught ReferenceError: require is not defined\nat ui-testing/login.spec.js:1:1\n\nReferenceError: require is not defined\n    at ui-testing/login.spec.js:1:1"
  }