karma.conf.js

// configures browsers to run test against
// any of [ 'ChromeHeadless', 'Chrome', 'Firefox' ]
const browsers = (process.env.TEST_BROWSERS || 'ChromeHeadless').split(',');

const singleStart = process.env.SINGLE_START;

// use puppeteer provided Chrome for testing
process.env.CHROME_BIN = require('puppeteer').executablePath();

const suite = 'test/testBundle.js';

module.exports = function(karma) {

  const config = {

    frameworks: [
      'webpack',
      'mocha',
      'sinon-chai'
    ],

    files: [
      suite
    ],

    preprocessors: {
      [ suite ]: [ 'webpack', 'env' ]
    },

    reporters: [ 'progress' ],

    coverageReporter: {
      reporters: [
        { type: 'lcovonly', subdir: '.' },
      ]
    },

    browsers,

    singleRun: true,
    autoWatch: false,

    webpack: {
      mode: 'development',
      resolve: {
        mainFields: [
          'module',
          'browser',
          'main'
        ],
        modules: [
          'node_modules',
          __dirname
        ]
      },
      module: {
        rules: [
          {
            test: /\.js$/,
            enforce: 'pre',
            use: [ 'source-map-loader' ]
          },
          {
            test: /\.(bpmn|css)$/,
            use: 'raw-loader'
          }
        ]
      },
      devtool: 'eval-source-map'
    }
  };

  if (singleStart) {
    config.browsers = [].concat(config.browsers, 'Debug');
    config.envPreprocessor = [].concat(config.envPreprocessor || [], 'SINGLE_START');
  }

  karma.set(config);
};