I know some states require ejected casings for tracking purposes on pistols, so every new semi or revolver in those states has been fired at least once.

I'd imagine most manufacturers of repute also test fire every weapon, but that'd be a guess on my part.

KG

It was stated in a TV tour of Smith&Wesson that each M&P pistol had one or more magazine loads fired prior to acceptance for shipping.

Berettas have at least one full magazine test fired.

I know not every company does this. I can't remember who it was, but a few years ago, this topic came up somewhere. And, apparently, some companies only check 1 out of every 100 guns, or something like that.