vue 单元测试

Question

vue 单元测试配置如下， 但是最后的结果如图，请问为什么会不出现被测试的组件呢？

specs

import Vue from 'vue'
import HelloWorld from '../../../examples/components/HelloWorld.vue'

describe('HelloWorld.vue', () => {
  it('should render correct contents', () => {
    const Constructor = Vue.extend(HelloWorld)
    const vm = new Constructor().$mount()
    expect(vm.$el.querySelector('.hello h1').textContent)
      .to.equal('Welcome to Your Vue.js App')
  })
})

index.js

import Vue from 'vue';

Vue.config.productionTip = false;

// require all test files (files that ends with .spec.js)
const testsContext = require.context('./specs', true, /\.spec$/);
testsContext.keys().forEach(testsContext);

// require all src files except main.js for coverage.
// you can also change this to match only the subset of files that
// you want coverage for.
const srcContext = require.context('../../examples', true, /^\.\/(?!main(\.js)?$)/);
let arr = srcContext.keys().filter(item => {
  return item !== './index.html'
})

arr.forEach(srcContext);

karma.config.js

// This is a karma config file. For more details see
//   http://karma-runner.github.io/0.13/config/configuration-file.html
// we are also using it with karma-webpack
//   https://github.com/webpack/karma-webpack

var webpackConfig = require('../../build/webpack.test.conf');

module.exports = function (config) {
  config.set({
    // to run in additional browsers:
    // 1. install corresponding karma launcher
    //    http://karma-runner.github.io/0.13/config/browsers.html
    // 2. add it to the `browsers` array below.
    browsers: ['PhantomJS'],
    frameworks: ['mocha', 'sinon-chai', 'phantomjs-shim'],
    reporters: ['spec', 'coverage'],
    files: ['./index.js'],
    preprocessors: {
      './index.js': ['webpack', 'sourcemap']
    },
    webpack: webpackConfig,
    webpackMiddleware: {
      noInfo: true,
    },
    coverageReporter: {
      dir: './coverage',
      reporters: [
        { type: 'lcov', subdir: '.' },
        { type: 'text-summary' },
      ]
    },
  });
};