private function assertSameInstances($className, Singleton $instance1, Singleton $instance2)
 {
     $this->assertTrue($instance1 === $instance2);
     $all = Singleton::getAllInstances();
     $this->assertTrue($instance1 === $all[$className]);
 }
 /**
  * @return CachePeer
  **/
 public function clean()
 {
     foreach (Singleton::getAllInstances() as $object) {
         if ($object instanceof GenericDAO) {
             $object->dropIdentityMap();
         }
     }
     return $this;
 }