I already run test subject. I'll probably be running both n ow. Might even cut a random 5+ drop for this. I love the shit out of designs like this, keep it coming Wizards. I can't believe how many cards in this set I'm already slotting in.
I'm not convinced this is a better card that test subject though. Subject wins topdeck wars and similarly super grindy games where this thing won't. Also, if you're holding a grip of counterspells and are even slightly behind on board, this might never flip where test subject would be inevitable. Test subject is also a pretty promo.