proof
1.The proof of the pudding is in the eating.只有通过体验才能判断事物的好坏
2.be living proof of sth./that （用行动或品格）证明...属实
tell
1.as far as i can tell据我判断
2.it's hard to tell这很难说
3.tell its own tale/story不言自喻，不释自明
4.tell tales (about sth./on sb.)
5.there's no telling难以预料，无法知道
6.you can never tell谁也拿不准，很难说