I\'m trying to run a same test across multiple browsers through for loop but it always run only on Firefox.
bros = [\'FIREFOX\',\'CHROME\',\'INTERNET EXPLORER\']
As Coretek said you need multiple webdriver instances. You will need to run the selenium-server .jar file and provide each one with an argument specifying the browser you want that instance of the server to run.
The argument for Internet Explorer is *iexplore, the argument for firefox is *firefox and the argument for chrome is *chrome. These are -forcedBrowserMode arguments. Otherwise selenium won't know what it should be running against. You may need to use *iexploreProxy for your tests, sometimes it works better than the *iexplore mode.
Check out this link for more arguments that may be useful:
http://seleniumforum.forumotion.net/t89-selenium-server-command-options-while-starting-server