The proof is in the pudding

the proof is in the pudding / 푸딩의 맛은 먹어봐야 안다
즉,실제로 시도하거나 사용해 보기 전까지는 그 성공 여부를 알 수 없다는 뜻
Paul: I wonder how useful those new books will be.

I guess the proof is in the pudding.

Brian: The proof is in the pudding? Are you sure?

I think we should examine them before we use them.

Paul: Of course I’ll look at them first, Brian.

I just meant that since we won’t know if they’re effective until we use them,

the proof will be in the pudding.

Brian: Paul, the proof is in the pudding.

Let’s throw it against the wall and see if it sticks.