Hmmmm, not sure that is right mate. If a shop refuses to test or even look at something for you then they shouldn't be open. I recently had a similar experience where I bought some products on line and one failed. I took it to MSY and they charged me 20 bucks to confirm it was faulty.
IMO if you turn business away you will not last. I will definitely be going back to the same store for my other computer stuff. Simple as that