MarketPress method of payment to capture credit card only

Hi, I am building a Proof of Concept site for a shopping cart. We do not have a merchant account but I want to demonstrate the ability to take a credit card as if it was real. Bogus card numbers are fine.

With other shopping carts I have the option of using a "Capture Only" type of card which is fine. However I am open to suggestions as to how to get the Proof of Concept without a real account available.