$GLOBALS['xoops']->path() and PHPUnit testing

[mambax7]

When testing with PHPUnit, this doesn't work (from \htdocs\kernel\config.php):

require_once $GLOBALS['xoops']->path('kernel/configoption.php');
require_once $GLOBALS['xoops']->path('kernel/configitem.php');

Changing it to this, made it work:

require_once __DIR__ . '/configoption.php';
require_once __DIR__ . '/configitem.php';

Should we change it everywhere to this? Or are the reason to not to do it, and is there a workaround for PHPUnit?