Gm 3.4 l v-6 camshaft

What is it doing? If you suspect the cam just check the cam position sensor signal. If the signal is OK and it's in time then the cam is OK. Or you can pull the cam sensor and look in to see if the cam is moving.

if you mean "how can I tell if my camshaft is really broken, (like my friend says it is) ?"

then I would pull the front valve cover and turn the engine by hand. If ALL the pushrods move up and down, the camshaft is not broken.

GW