phpunit:使用依赖项测试工厂类

我有下面的工厂类,它有一个依赖项$client。我将依赖项移动到工厂类,因为它第一次出现在service_service1类中,所以我可以测试该服务类。但是我怎样才能测试工厂的课程呢?

class Factory implements Service
{

    public static function factory($service)
    {
        $config = Zend_Registry::get('config');

        switch ($service) {
            case Service::Service1:
                $client = new Zend_Soap_Client(
                    $config->url,
                    array(
                        'encoding' => 'UTF-8'
                    )
                );
                $pickupPoint = new Service_Service1($client);
                break;
        }
    }
}