karma.conf.js

var webpack = require('webpack');

module.exports = function (config) {
    config.set({
        browsers: ['Chrome'],
        singleRun: true,
        frameworks: ['mocha'],
        files: [
            'tests.webpack.js'
        ],
        preprocessors: {
            'tests.webpack.js': ['webpack']
        },
        reporters: ['dots'],
        webpack: {
            module: {
                loaders: [{
                    test: /\.jsx?$/,
                    exclude: /node_modules/,
                    loader: 'babel-loader'
                }, {
                    test: /\.css$/,
                    loader: "style-loader!css-loader"
                }]
            },
            plugins: [
                new webpack.DefinePlugin({
                    'process.env': {
                        'NODE_ENV': JSON.stringify('test')
                    }
                })
            ],
            watch: true
        },
        webpackServer: {
            noInfo: true
        }
    });
};