Require dependencies when appropriate in some unit test files.

Previously, attempting to run certain test files in isolation would resultin
fatal errors, as the parent classes had not been loaded.

Props isaacchapman.
Fixes #32984.

git-svn-id: https://develop.svn.wordpress.org/trunk@33250 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/filesystem/find_folder.php

@@ -1,5 +1,7 @@
 <?php
 
+require_once dirname( __FILE__ ) . '/base.php';
+
 /**
  * @group filesystem
  * @group wp-filesystem