Test that it can find paths that use __DIR__

Author: Bellangelo

tests/files/file_exists_using_DIR.php

@@ -0,0 +1,8 @@
+<?php
+
+declare(strict_types=1);
+
+include __DIR__ . '/include_me_to_prove_you_work.txt';
+include_once __DIR__ . '/include_me_to_prove_you_work.txt';
+require __DIR__ . '/include_me_to_prove_you_work.txt';
+require_once __DIR__ . '/include_me_to_prove_you_work.txt';