public function add(IMinkDriverFactory $driver_factory)
	{
		$driver_name = $driver_factory->getDriverName();

		if ( isset($this->_registry[$driver_name]) ) {
			throw new \LogicException('Driver factory for "' . $driver_name . '" driver is already registered.');
		}

		$this->_registry[$driver_name] = $driver_factory;
	}