karma.conf.js

module.exports = function(config) {
  var karmaConfig = {
    frameworks: ['mocha', 'chai', 'sinon'],

    // list of files / patterns to load in the browser
    files: [
			'./node_modules/jquery/dist/jquery.min.js',
      './node_modules/lite-fixture/index.js',
      './test/unit/**/*.spec.js'
    ],

    client: {
      mocha: {
        opts: './mocha.opts'
      }
    },

    webpack: {
      devtool: 'inline-source-map',
      module: {
          rules: [
              {
                  test: /\.js$/,
                  exclude: /node_modules/,
                  loader: "babel-loader",
              }
          ]
      }
    },

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

    browsers: [],

    reporters: ['mocha'],
    webpackMiddleware: {
        noInfo: true
    }
  };

  karmaConfig.browsers.push(config.chrome ? "Chrome" : "ChromeHeadless");

  if(config.coverage) {
    karmaConfig.reporters.push('coverage-istanbul');
    karmaConfig.coverageIstanbulReporter = {
      reports: ["text-summary", "html", "lcovonly"],
      dir: './coverage'
    };
    karmaConfig.webpack.module.rules.unshift({
        test: /\.js$/,
        exclude: /(node_modules|test)/,
        loader: 'istanbul-instrumenter-loader'
    });
    karmaConfig.singleRun = true;
  }

  config.set(karmaConfig);
};