Please see if this paragraph helps: https://docs.codewars.com/training/training-example#debugging-a-kata

Hi! That's part of the learning experience. You can see some tests that your algorithm has to pass. Some tests are hidden. Your code has to work for any given input, you can't simply test every single possible input so you have got to refactor your code so that it works for every possible input.

where can i see all the tests my cod has to pass?
it passed one but then it says my code is missing two tests when i try to attempted...
thanks.

can anyone explain why do the last return is 0?
i dont get why it works like that, thanks