jupyterlab/tests/karma-cov.conf.js

const path = require('path');
const baseConf = require('./karma.conf');

module.exports = function(config) {
  baseConf(config);
  config.reporters = ['mocha', 'coverage-istanbul'];
  config.webpack.module.rules.push(
    // instrument only testing sources with Istanbul
    {
      test: /\.js$/,
      use: {
        loader: 'istanbul-instrumenter-loader',
        options: { esModules: true }
      },
      include: process.env.KARMA_COVER_FOLDER
    }
  );
  config.coverageIstanbulReporter = {
    reports: ['html', 'text-summary'],
    dir: path.join('.', 'coverage'),
    fixWebpackSourcePaths: true
  };
};