protected function _chmod()
{
self::$vfs->createFolder('', 'chmodtest');
self::$vfs->writeData('chmodtest', 'chmod', 'foo');
self::$vfs->changePermissions('chmodtest', 'chmod', '640');
$folder = self::$vfs->listFolder('chmodtest');
$this->assertEquals('-rw-r-----', $folder['chmod']['perms']);
}