karma.conf.js

const webpackConfig = require('./webpack.test');
const test = process.env.NODE_ENV === 'test';

module.exports = function(config) {
  config.set({
    plugins: [
      'karma-chrome-launcher',
      'karma-mocha',
      'karma-chai-plugins',
      'karma-sourcemap-loader',
      'karma-webpack',
      'karma-coverage',
      'karma-spec-reporter'
    ],

    autoWatch: test,

    webpack: webpackConfig,

    webpackMiddleware: {
      noInfo: true
    },

    client: {
      captureConsole: true
    },

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

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

    // preprocess matching files before serving them to the browser
    // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
    // run the bundle through the webpack and sourcemap plugins
    preprocessors: {
      'src/app.test.js': ['webpack', 'sourcemap']
    },

    // test results reporter to use
    // possible values: 'dots', 'progress'
    // available reporters: https://npmjs.org/browse/keyword/karma-reporter
    reporters: ['spec', 'coverage'],

    coverageReporter: {
      reporters: [
        { type: 'lcov', dir: 'coverage/', subdir: '.' },
        { type: 'json', dir: 'coverage/', subdir: '.' },
        { type: 'text-summary' }
      ]
    },

    // 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,

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

    // Continuous Integration mode
    // if true, Karma captures browsers, runs the tests and exits
    singleRun: !test
  });
};