public function pack(){

        try{
            //call the factory to get the itemPacker implementation
            $testPacker = $this->getTestPacker();

            //then create the pack
            $testPack = $testPacker->packTest($this->test);

        } catch(Exception $e){
            throw new common_Exception('The test '. $this->test->getUri() .' cannot be packed : ' . $e->getMessage());
        }

        return $testPack;
    }