http://watirmelon.com/2011/04/05/tryselenium-org-in-watir-webdriver/

try_selenium.rb

require 'rubygems'
require 'highline/import'
require 'watir-webdriver'

begin
  username = ask("What is your twitter username?")
  password = ask("and your password?") { |q| q.echo = false }
  browser=  Watir::Browser.start "twitter.com", :firefox
  browser.span(:text => "Sign in").click
  browser.text_field(:id => "username").set username
  browser.text_field(:id => "password").set password
  browser.button(:id => "signin_submit").click
  raise "Could not log into Twitter: either your password is wrong or a CAPTCHA is needed."   if browser.url.include? "sessions"
  100.times do |attempt|
    browser.text_field(:class => "twitter-anywhere-tweet-box-editor").when_present.set "#SeConf is awesome x #{attempt}! http://tryselenium.org @Watir-WebDriver is even more awesome!"
    browser.link(:class => "tweet-button button").when_present.click
    browser.goto "twitter.com"
  end
ensure
  browser.close
end