hoge.rb

require 'nokogiri'
require 'capybara'
require 'capybara/poltergeist'
class Hoge

  def self.scrape_include_js_contents
    #poltergistの設定
    Capybara.register_driver :poltergeist do |app|
      Capybara::Poltergeist::Driver.new(app, {:js_errors => true }) #追加のオプションはググってくださいw
    end
    Capybara.default_selector = :xpath
    session = Capybara::Session.new(:poltergeist)
    #自由にUser-Agent設定してください。
    session.driver.headers = { 'User-Agent' => "mozilla/5.0 (iphone; cpu iphone os 5_1_1 like mac os x) applewebkit/534.46 (khtml, like gecko) mobile/9b206 micromessenger/5.0" } 
    # Need large integer when page is long
    session.driver.resize_window(1080, 108000)
    session.visit "https://www.google.com"
    session.save_screenshot('screenshot.png', :full => true)
    # parse html content with nokogiri later
    page = Nokogiri::HTML.parse(session.html)
  end 
end