DummyPrivateStreamWrapper.php

<?php

declare (strict_types=1);
namespace Drupal\file_test\StreamWrapper;

use Drupal\Core\Url;

/**
 * Helper class for testing the stream wrapper registry.
 *
 * Dummy stream wrapper implementation (dummy-private://).
 */
class DummyPrivateStreamWrapper extends DummyStreamWrapper {
  
  /**
   * {@inheritdoc}
   */
  public function getExternalUrl() : string {
    $path = str_replace('\\', '/', $this->getTarget());
    return Url::fromRoute('file_test.dummy', [
      'filepath' => $path,
    ], [
      'absolute' => TRUE,
      'path_processing' => FALSE,
      'query' => [
        'file' => $path,
      ],
    ])->toString();
  }

}