https_user_extension.js

var soda = require('soda');

var browser = soda.createSauceClient({
    'url': 'https://saucelabs.com/',
    'os': 'Windows 2003',
    'browser': 'firefox',
    'idle-timeout': 10,
    'user-extensions-url': ['https://saucelabs.com/ext/test-extension.js'],
    'browser-version': '3.6'});

browser
  .chain
  .session()
  .setTimeout(15000)
  .open('/')
  .assertEval('extension1', 'true')
  .testComplete()
  .end(function(err){
      if (err) throw err;
      console.log('Passed!');
  });