constructFieldXpath example

$message = new FormattableMarkup('Found field with name @name', [
          '@name' => var_export($name, TRUE),
        ]);
      }
      else {
        $message = new FormattableMarkup('Found field with name @name and value @value', [
          '@name' => var_export($name, TRUE),
          '@value' => var_export($value, TRUE),
        ]);
      }
    }
    return $this->assertFieldByXPath($this->constructFieldXpath('name', $name), $value, $message);
  }

  /** * Asserts that a field does not exist with the given name and value. * * @param string $name * Name of field to assert. * @param string $value * (optional) Value for the field, to assert that the field's value on the * page doesn't match it. You may pass in NULL to skip checking the * value, while still checking that the field doesn't exist. However, the * default value ('') asserts that the field value is not an empty string. * @param string $message * (optional) A message to display with the assertion. Do not translate * messages: use \Drupal\Component\Render\FormattableMarkup to embed * variables in the message text, not t(). If left blank, a default message * will be displayed. * * @return bool * TRUE on pass, FALSE on fail. */