使用ActiveMerchant和PayPal在实际网站上接受虚拟信用卡

I'm setting up a rails site that will accept credit cards with ActiveMerchant and PayPal Website Payments Pro. I am successfully testing against the PayPal sandbox, but need to be able to test on my live site as well. I'd like to implement a solution whereby registrations on my live site with email addresses from my own domain use the PayPal sandbox, but for everyone else it uses the live PayPal site. That way when I test my live site I'm not paying myself and getting taxed by PayPal in the process :-)I'm setting up a rails site that will accept cr