Hacky Testing Firefox extension with Selenium Webdriver

e2e.js

const { Builder, By, Key, until } = require('selenium-webdriver');
const firefox = require('selenium-webdriver/firefox');
const Command = require('selenium-webdriver/lib/command').Command;
const path = require('path');

const options = new firefox.Options()
  .setPreference('extensions.firebug.showChromeErrors', true);

(async function example() {
  let driver = await new Builder()
    .forBrowser('firefox')
    .usingServer('http://localhost:4444/wd/hub')
    .setFirefoxOptions(options)
    .build();
  const addonId = await installWebExt(driver, '/path/to/extension.xpi');

  try {
    const baseUrl = await getBaseUrl(driver, addonId);
    const newTabUrl = baseUrl + 'index.html';
    await driver.get(newTabUrl); 
    // I can now interact with the newtab page at this point 
    
    await driver.sleep(5000);
  } finally {
    await driver.quit();
  }
})();

async function installWebExt(driver, extension) {
  let session = await driver.session_;
  let cmd = new Command('moz-install-web-ext')
    .setParameter('path', path.resolve(extension))
    .setParameter('sessionId', session.getId())
    .setParameter('temporary', true);

  let executor = driver.getExecutor();
  executor.defineCommand(cmd.getName(), 'POST', '/session/:sessionId/moz/addon/install');
  return executor.execute(cmd);
}

async function getBaseUrl(driver, addonId) {
  await driver.get('about:memory');
  const button = await driver.findElement(By.id('measureButton'));
  button.click();
  await driver.sleep(3000);
  const elements = await driver.findElements(By.css('[title="WebExtensions that are active in this session"]'))
  const text = await Promise
    .all(elements.map(element => element.getText()))
    .then(texts => 
      texts.find(text => text.indexOf(addonId) > 0)
    );

  if (text) {
    return text.match(/baseURL=([^\), ]+)/)[1];
  }
  return null;
}

manifest.json

{
  "manifest_version": 2,
  "short_name": "Foo",
  "name": "Foo",
  "description": "Foo",
  "version": "0.1.0",

  "chrome_url_overrides" : {
    "newtab": "index.html"
  },
}