Use webpack with karma


npm install --save-dev karma-webpack
// Karma configuration 
module.exports = function(config) {
        // ... normal karma configuration 
        files: [
            // all files ending in "_test" 
            // each file acts as entry point for the webpack configuration 
        preprocessors: {
            // add webpack as preprocessor 
            'test/*_test.js': ['webpack'],
            'test/**/*_test.js': ['webpack']
        webpack: {
            // karma watches the test entry points 
            // (you don't need to specify the entry option) 
            // webpack watches dependencies 
            // webpack configuration 
        webpackMiddleware: {
            // webpack-dev-middleware configuration 
            // i. e. 
            noInfo: true
        plugins: [

This configuration is more performant, but you cannot run single test anymore (only the complete suite).

The above configuration generate a webpack bundle for each test. For many testcases this can result in many big files. The alterative configuration creates a single bundle with all testcases.

        files: [
            // only specify one entry point 
            // and require all tests in there 
        preprocessors: {
            // add webpack as preprocessor 
            'test/test_index.js': ['webpack']
// test/test_index.js 
// require all modules ending in "_test" from the 
// current directory and all subdirectories 
var testsContext = require.context(".", true, /_test$/);

Every test file is required using the require.context and compiled with webpack into one test bundle.

You can use the karma-sourcemap-loader to get the source maps generated for your test bundle.

npm install --save-dev karma-sourcemap-loader

And then add it to your preprocessors

preprocessors: {
    'test/test_index.js': ['webpack', 'sourcemap']

And tell webpack to generate sourcemaps

webpack: {
  // ... 
    devtool: 'inline-source-map'

This is the full list of options you can specify in your Karma config.

Webpack configuration.

Configuration for webpack-dev-middleware.

Copyright 2014-2015 Tobias Koppers