Faulty handheld, store wants to take it away for testing rather than just replace

Buzby

Your entitlement is only valid if they agree. By getting it back boxed, when the fault is found they can process the refund immediately as there is nothing else you need do.

Without them bring given the chance to check it (they may be unable to do this the moment you drop it off) you may end up shooting yourself in the foot by not giving them a reasonable opportunity to agree with your findings.

I'd give then 3 days max - anything less is unreasonable.