karma-bs.config.js

const originalConfigFn = require('./karma.conf.js');

let originalConfig;
originalConfigFn({ set: (config) => { originalConfig = config; } });

if (!process.env.BROWSER_STACK_USERNAME || !process.env.BROWSER_STACK_ACCESS_KEY) {
  throw new Error(`
    !!You have to set your Browserstack automate username and key!!

    Login and go to https://www.browserstack.com/accounts/settings
    then run in your console (or add it to your ~/.bashrc)

    export BROWSER_STACK_USERNAME=[username];
    export BROWSER_STACK_ACCESS_KEY=[key];
  `);
}

module.exports = (config) => {
  config.set({
    ...originalConfig,

    browserStack: {
      username: process.env.BROWSER_STACK_USERNAME,
      accessKey: process.env.BROWSER_STACK_ACCESS_KEY,
      project: 'open-wc',
    },

    browsers: [
      'bs_win10_chrome_69',
      'bs_win10_firefox_62',
      // 'bs_win10_ie_11',
    ],

    // define browsers
    customLaunchers: {
      bs_win10_chrome_69: {
        base: 'BrowserStack',
        browser: 'Chrome',
        browser_version: '69.0',
        os: 'Windows',
        os_version: '10',
      },
      bs_win10_firefox_62: {
        base: 'BrowserStack',
        browser: 'Firefox',
        browser_version: '62.0',
        os: 'Windows',
        os_version: '10',
      },
      bs_win10_ie_11: {
        base: 'BrowserStack',
        browser: 'IE',
        browser_version: '11.0',
        os: 'Windows',
        os_version: '10',
      },
    },
  });
};