Hire someone to kill the magician. If he can make people immortal, he would do it to himself.
EitherAlso, you aren't really immortal, are you? Anything that destroys your head, throat ofor stomach will kill you. so, if the magician wanted to do you harm, he doesn't need to trick you at all.
But really, what would be the purpose of testing it? whatWhat suicidal thing would you regret not having done because you mistakenly believed it would be fatal? Saving someone you weren't willing to risk your life for?