You need these when using only javascript_session: selenium2 so you need selenium server running behind. Check other posts in Selenium section of this blog to see how you can run selenium server.


Behat.yml


# Add "-p firefox" parameter to behat command to run tests with Firefox browser
firefox:
extensions:
Behat\MinkExtension\Extension:
browser_name: firefox

# Add "-p chrome" parameter to behat command to run tests with Chrome browser
chrome:
extensions:
Behat\MinkExtension\Extension:
browser_name: chrome

# Add "-p safari" parameter to behat command to run tests with Safari browser
safari:
extensions:
Behat\MinkExtension\Extension:
browser_name: safari