#
  # Macro that creates a test asserting that the controller sends the
  # content type given.
  # Example:
  #
  #   should_send_content_type :pdf
  #   should_send_content_type :csv
  def should_send_content_type(content_type)
   should "send content type #{content_type}" do
     assert_equal Mime::Type.lookup_by_extension(content_type.to_s).to_s,
                  @response.content_type
   end
  end