Preen! Donatello gives him a nod. "Right, okay. Uh..."

'Still testing' doesn't really inspire confidence but he also knows it's a vital part of making sure anything works, especially when it comes to science, so he doesn't fuss about it. He'll just...hold his breath because he's not sure how still he's expected to be, but he'd rather not break Steven's concentration during something like casting a spell.