Poltergeist RSpec screenshot

screenshot.rb

# spec/support/screenshot.rb
RSpec.configure do |config|

  # A work-around to support accessing the current example that works in both
  # RSpec 2 and RSpec 3.
  fetch_current_example = RSpec.respond_to?(:current_example) ?
    proc { RSpec.current_example } : proc { |context| context.example }

  config.after do
    example = fetch_current_example.call(self)
    if screenshot = example.metadata[:screenshot]
      filename = if screenshot.is_a? String
        screenshot
      else
        example.full_description.parameterize('_')
      end
      page.save_screenshot("spec/images/#{filename}.png", full: true)
    end
  end

end