WPSelenium is a library that allows you to quickly get up and running testing your site with selenium and phpunit.
It does this by installing and configuring phpunit, the selenium server, the php client webdriver (by facebook) and the correct drivers for the browser you want to test on. Once installed all you have to worry about is writing your selenium php tests.
composer require --dev devchid/wpselenium
As you would a phpunit test using the facebook webclient driver
composer /vendor/bin/wpselenium chrome