protected function tearDown()
 {
     parent::tearDown();
     if (!self::$_entityTablesCreated) {
         return;
     }
     $em = $this->_getEntityManager();
     $classes = array();
     foreach (self::$_entityTablesCreated as $className => $flag) {
         $classes[] = $em->getClassMetadata($className);
     }
     $this->_getSchemaTool()->dropSchema($classes);
     self::$_entityTablesCreated = array();
 }