Hi, I'm a student from China.There are many Online Judge Platforms in China have there test data open and transparent, such as Luogu(www.luogu.com.cn), LibreOJ(loj.ac), Universal OJ(uoj.ac). Futhermore, Codeforces also keeps their testdata open. They all share their test data to some extent. I think it's a very important supporting role when coding. If the official doesn't show the data, no one knows the correctness of it. There are some problems with wrong data/wrong special judge in UVa, as we all know. And I don't agree that spending all day on guessing "Where am I wrong" is a goodway to study.
In a word, I'd like to suggest that developing a function that we users could see the test data we failed. I have to say, it's very, very, very important to us.