class DummyStreamWrapper

class DummyStreamWrapper extends LocalStream {
  
  /**
   * {@inheritdoc}
   */
  public function getName() {
    return t('Dummy files');
  }
  
  /**
   * {@inheritdoc}
   */
  public function getDescription() {
    return t('Dummy wrapper for simpletest.');
  }
  public function getDirectoryPath() {
    return \Drupal::getContainer()->getParameter('site.path') . '/files';
  }
  
  /**
   * Override getInternalUri().
   *
   * Return a dummy path for testing.
   */
  public function getInternalUri() {
    return '/dummy/example.txt';
  }
  
  /**
   * Override getExternalUrl().
   *
   * Return the HTML URI of a public file.
   */
  public function getExternalUrl() {
    return '/dummy/example.txt';
  }

}