If you want to run it on phantomjs (a headless browser) you can add this profile to your behat.yml and you need phantomjs >= 1.8.0
phantomjs:
    extensions:
        Behat\MinkExtension\Extension:
            base_url: http://dev.local
            goutte: ~
            selenium2:
 wd_host: "http://localhost:8643/wd/hub"