Hello. Sorry i forgot to specify. I used Javascript to solve it. At the end i returned "" instead of none.

Thanks for this, Candice. I couldn't find out what was wrong with my solution but i checked your question and also changed the final return of my function from "none" to " ". So, this makes me think that the problem is with the test case.

Hello, everyone. I tried to do the exercise but it failed miserably, so i tried another solution and gladly almost all tests passed except for one of them. The test where the string is 'abba', it says it should return "none" but my solution returns " " (nothing) but I tested it in my computer and the return is the expected value ("none") with strings where all characters are repeated.

This is the test where it fails: should handle all repeating strings
abba -> expected 'none' to equal ' '

Even though the exercise was entertaining.