Detecting flashes in Ruby

common_steps.rb

# A generic step to detect for a flash, currently either an alert or a notice (called a notification)                                                                         
# Usage should be:
# I should see [notification title] [titletype]
#
# Notification titles are defined within $ROOT/features/support/flashes.rb
Then /^I should see ([^"]*) (alert|notification)$/ do |name, type|
  within "div#flash-#{type}" do
    page.should have_content flash_of(name)
  end 
end

support_flashes.rb

module FlashHelpers
  # Maps a name to a flash message.
  def flash_of(flash_name)
    case flash_name

    when /^invalid sign in$/
      'Invalid username or password.'

    else
      raise "Can't find mapping for \"#{flash_name}\" to a flash message:.\n" +
        "Now, go and add a mapping in #{__FILE__}"
    end
  end
end

World(FlashHelpers)