karma.conf.js

const webpackCfg = require('./webpack.config'),
  path = require('path');

// Set node environment to testing
process.env.NODE_ENV = 'test';

module.exports = function(config) {
  config.set({
    basePath: '',
    browsers: ['ChromeHeadless'],
    customLaunchers: {
      ChromeHeadless: {
        base: 'Chrome',
        flags: [
          '--no-sandbox',
          '--headless',
          '--disable-gpu',
          '--remote-debugging-port=23366'
        ]
      }
    },
    files: ['test/loadtests.js'],
    port: 8000,
    captureTimeout: 60000,
    frameworks: ['mocha', 'chai'],
    client: {
      mocha: {}
    },
    singleRun: true,
    reporters: ['mocha', 'coverage'],
    preprocessors: {
      'test/loadtests.js': ['webpack', 'sourcemap']
    },
    webpack: webpackCfg,
    webpackServer: {
      noInfo: true
    },
    coverageReporter: {
      // specify a common output directory
      dir: path.join(__dirname, 'coverage'),
      reporters: [
        { type: 'html', subdir: 'report-html' },
        { type: 'lcovonly', subdir: '.', file: 'report-lcovonly.txt' },
        { type: 'text' }
      ]
    }
  });
};