# File test/test_document.rb, line 107
      def filter_open(context, script_name, request, response, logger)
        @parent.filter_open(context, script_name, request, response, logger)
        response.status = 404  # Not Found
        response.set_header('Content-Type', 'text/html')
        response.start_body
        response << "<html>bar</html>\n"
        terminate_filter       # skip to filter_close.
        nil
      end