In addition to the npm package, you will to download the WebDriver implementations you wish to utilize. As of 2.34.0, browserstack-webdriver natively supports the ChromeDriver. Simply download a copy and make sure it can be found on your PATH. The other drivers (e.g. Firefox, Internet Explorer, and Safari), still require the standalone Selenium server. To run the tests, you will need to download a copy of the ChromeDriver and make sure it can be found on your PATH.