trial and error
noun [ U ] uk/ˌtraɪəl ənd ˈer.ər/ us/ˌtraɪəl ənd ˈer.ɚ/
C2 反复试验，试错法
a way of achieving an aim or solving a problem by trying a number of different methods and learning from the mistakes that you make
There's no instant way of finding a cure - it's just a process of trial and error. 找到治疗方案不可能一蹴而就——这只能是一个反复试验的过程。