/**
  * Add the given array of member extensions as class names.
  * This is useful for re-adding extensions after being removed
  * in a test case to produce an unbiased test.
  *
  * @param array $extensions
  * @return array The added extensions
  */
 protected function addExtensions($extensions)
 {
     if ($extensions) {
         foreach ($extensions as $extension) {
             Member::add_extension($extension);
         }
     }
     return $extensions;
 }