Preprocess source code by espower-source
npm install karma-espower-preprocessor --save-dev I'm recommend to use with karma-sourcemap-loader if you use some altJS.
// karma.conf.js module.exports = function(config) { config.set({ preprocessors: { '**/*.js': ['espower'] // '**/*.js': ['sourcemap', 'espower'] }, espowerPreprocessor: { options: { // emit espowerified code. // default: false (in-memory) emitActualCode: true, // ignore upstream SourceMap info. // default: false ignoreUpstreamSourceMap: false }, transformPath: function(path) { // default return path.replace(/\.js$/, '.espowered.js'); } } }); };