reverted:
--- b/core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7Test.php
+++ a/core/modules/migrate_drupal_ui/tests/src/Functional/d7/Upgrade7Test.php
@@ -69,24 +69,6 @@
     return __DIR__ . '/files';
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  protected function getSourcePrivateFilePath() {
-    return __DIR__ . '/private';
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function getFilenames() {
-    return [
-      'public' => ['cube.jpeg', 'ds9.txt'],
-      'private' => ['Babylon5.txt'],
-      'temporary' => ['TerokNor.txt'],
-    ];
-  }
-
   /**
    * {@inheritdoc}
    */