Rails3 configuration example for using selenium grid

selenium_grid.rb

# -*- coding: utf-8 -*-
require 'spork'
require 'socket'

Spork.prefork do
  require 'cucumber/rails'

  # read environment variables
  desired_capabilities = {
    browserName: (ENV['SELENIUM_DESIRED_BROWSER_NAME'] or "firefox"),
    version: ENV['SELENIUM_DESIRED_VERSION'],
    platform: ENV['SELENIUM_DESIRED_PLATFORM'],
  }
  if ENV['SELENIUM_HUB_URL']
    selenium_hub_url = ENV['SELENIUM_HUB_URL']
  elsif ENV['JENKINS_URL']
    uri = URI(ENV['JENKINS_URL'])
    selenium_hub_url = "#{uri.scheme}://#{uri.host}:4444/wd/hub"
  else
    selenium_hub_url = "http://127.0.0.1:4444/wd/hub"
  end

  # guess ip address that external www browsers can connect
  # see http://coderrr.wordpress.com/2008/05/28/get-your-local-ip-address/
  do_not_reverse_lookup = Socket.do_not_reverse_lookup
  begin
    Socket.do_not_reverse_lookup = true
    server_host = UDPSocket.open do |socket|
      socket.connect(URI(selenium_hub_url).host, 4444)
      socket.addr.last
    end
  ensure
    Socket.do_not_reverse_lookup = do_not_reverse_lookup
  end

  # intercept WebMock
  if defined?(WebMock) && !WebMock.net_connect_allowed?(selenium_hub_url)
    # currently we can't help choosing dirty solution
    if WebMock::Config.instance.allow
      raise RuntimeError.new "WebMock::Config.instance.allow is present: #{WebMock::Config.instance.allow}"
    end
    options = {
      allow_localhost: WebMock::Config.instance.allow_localhost,
      allow: selenium_hub_url,
      net_http_connect_on_start: WebMock::Config.instance.net_http_connect_on_start,
    }
    WebMock.disable_net_connect! options
  end

  # configure capybara
  Capybara.default_selector = :css
  Capybara.default_driver = :selenium
  Capybara.register_driver :selenium do |app|
    Capybara::Selenium::Driver.new(app,
      :browser => :remote,
      :url => selenium_hub_url,
      :desired_capabilities => desired_capabilities,
      )
  end
  server_port = Capybara.current_session.driver.rack_server.port
  Capybara.app_host = "http://#{server_host}:#{server_port}"
end