The proof of pudding is in the eating 英文諺語
The proof of pudding is in the eating 空言不如力行
You can only judge the quality of something after you have tried, used, or experienced it; to fully test something you need to experience it for yourself.
The idiom is usually stated as “the proof is in the pudding” and means that the end result is the mark of the success or failure of one’s efforts or planning. The phrase may also be used in the past and future tenses: the proof will be/was in the pudding. You can only say something is a success after it has been tried out or used.
“We think we’ve been productive over the last two weeks but the proof is in the pudding on Sunday.”