This is just a suggestion for a new feature. When I played don’t panic, I created a code that got me through a couple of tests. I got greedy and did last moment modification to pass more tests and as a result I lost some of the test which I already accomplished with the previous version of the code. So I thought, that misfortune would have been avoided if I had a quick handy feature to save my code.
The idea:
Give each contestants 3 or 5 slots to save their code. So I’m doing a challenge and I create code that makes me past 5/10 of the tests. I want to pass more, but I don’t want to risk what I already have. So I click save in slot and I’m prompted to name the save, so I name it “Code that passed 5/10 tests” to keep track of why I saved that code.
Second idea:
This idea is more awesome but require more work on codingame staff 
First, a “play against all tests” button. With this button you can do all of them in an autoplay fashion. One by one and see the results.
Second, each time you use this button the platform will keep track of the score and always save your highest score and also the code that got it, so when the time is almost finished and your current code is not your best, the platform will prompt and ask you if you want to use the code that got you the best score so far. I think it’s doable and may not be that hard to implement. 
Cheers