Comment by brendoelfrendo

You cannot, under any circumstances, keep a real card # and use it as test data. I think that's where this conversation is getting hung up, because the idea of running a transaction through prod and them doing the same in test to see if it matches isn't something you can do. I mean, of course you can throw the prices and UPCs at the new system and verify that the new system's math matches the old system, but that's only the most basic function of a POS system. Testing a transaction from end-to-end would have to be done with synthetic data in an isolated environment, and I'll assume that's what OP is trying to articulate.