Issue #3241272 by andypost, alexpott:...

Issue #3241272 by andypost, alexpott: core/modules/system/tests/src/Functional/FileTransfer/TestFileTransfer.php causes deprecations on PHP 8.1

core/modules/system/tests/src/Functional/FileTransfer/TestFileTransfer.php

@@ -8,10 +8,26 @@
  * Mock FileTransfer object for test case.
  */
 class TestFileTransfer extends FileTransfer {
-  protected $host = NULL;
-  protected $username = NULL;
-  protected $password = NULL;
-  protected $port = NULL;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $host = '';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $username = '';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $password = '';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $port = 0;
 
   /**
    * This is for testing the CopyRecursive logic.