Take a screenshot

Asset.rb

# first install 'selenium-webdriver'gem
require 'selenium-webdriver'
 width = 800
 height = 600
 driver = Selenium::WebDriver.for :firefox
 driver.navigate.to 'http://localhost:3000'
 driver.execute_script %Q{
   window.resizeTo(#{width}, #{height});
 }
 driver.save_screenshot('/tmp/screenshot.png')
 driver.quit