Any thoughts which theories Harry tested with

"Is that a usual tactic, by the way?" Harry said, voice still odd. "Carrying something large Transfigured into something small to use as a weapon? Or is that a usual exercise for Transfiguration practice?"

He tested whether Dumbledore anticipated his use of the rock when he told him to carry it around. He's looking for explanations of all the early behavior where Dumbledore pretended to be mad, since he now believes that while Dumbledore may have wrong and even "mad" beliefs, he only does things like burning chickens to mess with people.