Another "trick" I've been taught it to tap the shaft on a hard part of your hand or wrist...you can almost HEAR a feint "rattle" if there is any crack.
Saw a shop owner once break one over his leg to show a doubting Thomas they don't "splinter" like polturded shafts.
That GT broke as clean as if cut on a saw!
Using their old nocks with allen sets, I did split out a nock end once...hair line crack. Thankfully, I had them crown dipped adn thought there was a "literal" hair on the area between feathers. Nope. Glasses on and my nail caught in the "crack".
T'mater stake right there. Seen some shafts blow and go thru guys arms... wood mostly, but a few old carbons. Nah. I'll test em good!