karma.conf.js

require('babel-core/register');

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

    frameworks: [
      'mocha'
    ],

    reporters: [
      'spec',
      'coverage'
    ],

    files: [
      'node_modules/phantomjs-polyfill/bind-polyfill.js',
      'tests/**/*_spec.*'
    ],

    preprocessors: {
      'tests/**/*_spec.*': ['webpack', 'sourcemap']
    },

    browsers: [
      'PhantomJS'
    ],

    singleRun: true,

    coverageReporter: {
      dir: 'build/coverage/',
      type: 'html'
    },

    webpack: require('./webpack.config'),

    webpackMiddleware: {
      noInfo: true
    }

  });
};

webpack.config.js

var path = require('path');
var webpack = require('webpack');
var merge = require('webpack-merge');
var HtmlwebpackPlugin = require('html-webpack-plugin');

var TARGET = process.env.npm_lifecycle_event;
var ROOT_PATH = path.resolve(__dirname);
var APP_PATH = path.resolve(ROOT_PATH, 'app');
var BUILD_PATH = path.resolve(ROOT_PATH, 'build'); 
var TEST_PATH = path.resolve(ROOT_PATH, 'tests');

process.env.BABEL_ENV = TARGET;


var common = {
  entry: APP_PATH,
  resolve: {
    extensions: ['', '.js', '.jsx']
  },
  module: {
    loaders: [
      {
        test: /\.jsx?$/,
        loaders: ['babel'],
        include: APP_PATH
      }
    ]
  },
  plugins: [
    new HtmlwebpackPlugin({
      title: 'React Setup'
    })
  ]
};

if (TARGET === 'start' || !TARGET) {
  module.exports = merge(common, {
    devtool: 'eval-source-map',
    devServer: {
      historyApiFallback: true,
      inline: true,
      progress: true,
      host: process.env.HOST,
      port: process.env.PORT
    }
  });
}

if (TARGET === 'test' || TARGET === 'tdd') {
  module.exports = merge(common, {
    entry: {},
    output: {},
    devtool: 'inline-source-map',
    resolve: {
      alias: {
        app: APP_PATH
      }
    },
    module: {
      preLoaders: [
        {
          test: /\.jsx?$/,
          loaders: ['isparta-instrumenter'],
          path: APP_PATH
        }
      ],
      loaders: [
        {
          test: /\.jsx?$/,
          loaders: ['babel'],
          path: TEST_PATH
        }
      ]
    }
  });
}