An example of karma with karma-webpack

karma.conf.js

var webpackConfig = require('./webpack.config')

module.exports = function (config) {
  // prep your webpack config for karma
  delete webpackConfig.entry
  webpackConfig.devtool = 'cheap-inline-source-map'

  config.set({
    // standard karma things
    basePath: '.',
    frameworks: ['mocha', 'sinon'],
    reporters: ['progress'],
    autoWatch: true,
    browsers: ['Chrome'],
    logLevel: config.LOG_INFO,

    // webpack
    files: [
      'testMain.js'
    ],
    preprocessors: {
      'testMain.js': ['webpack', 'sourcemap']
    },
    webpack: webpackConfig,
    webpackServer: {
      noInfo: false,
      progress: true
    }
  })
}

testMain.js

let testsContext = require.context('./tests', true, /Test$/)
testsContext.keys().forEach(testsContext)