cleanup for self-review

tests/PHPUnit/CustomAffixes/@#$%^&()-_=+.php

@@ -1,6 +1,10 @@
 <?php
 
-test(sprintf('this runs file names like "%s"', basename(__FILE__)))
-    ->assertTrue(true);
+/*
+ * NOTE: To preserve cross-platform testing compatibility we cannot use ! * and
+ * other Windows reserved characters in this test's filename.
+ *
+ * See https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#naming-conventions
+ */
 
-    //!@#$%^&*()-_=+
+it(sprintf('runs file names like `%s`', basename(__FILE__)))->assertTrue(true);