firefox_profile.rb

#Setup Firefox profile to use proxy
profile = Selenium::WebDriver::Firefox::Profile.new
profile["network.proxy.type"]          = 1
profile["network.proxy.http"]          = "127.0.0.1"
profile["network.proxy.http_port"]     = 9001

#Add urls to be exluded from Black Hole proxy
profile["network.proxy.no_proxies_on"] = "localhost, 127.0.0.1"

#Add profile to options
options[:profile]                                 = profile

#Create browser
browser = Selenium::WebDriver.for :firefox, options