protected function _message(&$data = [], $message =  null) {
		if (!empty($data[0])) {
			foreach ($data as $key => $value) {
				$message = (!empty($data[$key][0])) ? $message : null;
				$message .= $this->_message($value, $message);
				unset($data[$key]);
			}
			return $message;
		}
		$defaults = ['trace' => null, 'expected' => null, 'result' => null];
		$data = (array) $data + $defaults;

		$message = null;
		if (!empty($data['trace'])) {
			$message = sprintf("trace: %s\n", $data['trace']);
		}
		if (is_object($data['expected'])) {
			$data['expected'] = get_object_vars($data['expected']);
		}
		if (is_object($data['result'])) {
			$data['result'] = get_object_vars($data['result']);
		}
		return $message . sprintf("expected: %s\nresult: %s\n",
			print_r($data['expected'], true),
			print_r($data['result'], true)
		);
	}