以下为 Karma 配置的一些详细代码。
1.文件结构

│  .gitignore
│  karma.conf.js
│  package.json
│  README.md
│  yarn.lock
│  
├─coverage
│  │  lcov.info
│  │  
│  ├─html
│  │      base.css
│  │      index.html
│  │      prettify.css
│  │      prettify.js
│  │      sort-arrow-sprite.png
│  │      sorter.js
│  │      utils.js.html
│  │      
│  └─lcov-report
│          base.css
│          index.html
│          prettify.css
│          prettify.js
│          sort-arrow-sprite.png
│          sorter.js
│          utils.js.html
│      
├─src
│      utils.js
│      
└─test
        utils.spec.js

2.package.json

{
  "devDependencies": {
    "babel-core": "^6.26.0",
    "babel-loader": "^7.1.2",
    "babel-plugin-istanbul": "^4.1.5",
    "babel-preset-env": "^1.6.1",
    "install": "^0.10.1",
    "istanbul-instrumenter-loader": "^3.0.0",
    "jasmine-core": "^2.8.0",
    "karma": "^1.7.1",
    "karma-chrome-launcher": "^2.2.0",
    "karma-coverage-istanbul-reporter": "^1.3.0",
    "karma-jasmine": "^1.1.0",
    "karma-phantomjs-launcher": "^1.0.4",
    "karma-webpack": "^2.0.5",
    "webpack": "^3.8.1"
  },
  "dependencies": {}
}

3.karma.conf.js

// Karma configuration
// Generated on Sun Nov 05 2017 16:19:33 GMT+0800 (中国标准时间)

module.exports = function(config) {
  config.set({

    // base path that will be used to resolve all patterns (eg. files, exclude)
    basePath: '',


    // frameworks to use
    // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
    frameworks: ['jasmine'],


    // list of files / patterns to load in the browser
    files: [
      './src/**/*.js',
      './test/**/*.spec.js',
    ],


    // list of files to exclude
    exclude: [
    ],


    // preprocess matching files before serving them to the browser
    // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
    preprocessors: {
      './src/**/*.js':['webpack'],
      './test/**/*.spec.js':['webpack']
    },

    webpack:{
      module: {
        rules: [{
          test: /\.js$/,
          use: {
              loader: 'istanbul-instrumenter-loader',
              options: { esModules: true }
          },
          enforce: 'pre',
          exclude: /node_modules|\.spec\.js$/,
        },
        {
          test: /\.js$/,
          use: {
              loader: 'babel-loader',
              options: {
                  presets: ['env'],
                  plugins: ['istanbul']
              }
            },
            exclude: /node_modules/
        }]
      }
    },
    

    // test results reporter to use
    // possible values: 'dots', 'progress'
    // available reporters: https://npmjs.org/browse/keyword/karma-reporter
    reporters: ['coverage-istanbul'],
    coverageIstanbulReporter: {
      reports: ['html', 'text-summary'],
      dir: 'coverage/',
      fixWebpackSourcePaths: true,
      skipFilesWithNoCoverage: true,
      'report-config': {
        html: {
          subdir: 'html'
        }
      }
    },

    // web server port
    port: 9876,


    // enable / disable colors in the output (reporters and logs)
    colors: true,


    // level of logging
    // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
    logLevel: config.LOG_INFO,


    // enable / disable watching file and executing tests whenever any file changes
    autoWatch: false,


    // start these browsers
    // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
    browsers: ['PhantomJS'],


    // Continuous Integration mode
    // if true, Karma captures browsers, runs the tests and exits
    singleRun: true,

    // Concurrency level
    // how many browser should be started simultaneous
    concurrency: Infinity
  })
}

4.utils.js

function add(x){
    return(y)=>{
        return x + y
    }
}

export {
    add
}

5.utils.spec.js

import { add } from "../src/utils"

describe("测试算数运算",()=>{
    it("测试加法运算",()=>{
        const add5 = add(5)
        expect(add5(5)).toBe(10)
    })
})

完。