The input will always be a 4 digit string

There is a fixed test for 21st century, and some other fixed tests were commented out.

In the case I mentioned above, you could think sorting alphabetically without distinction between capital and lowercase letters. Check this other post: https://www.codewars.com/kata/57cfdf34902f6ba3d300001e/discuss#64a5b40cdddc251219dfa1de

It includes the information about ASCII chars, because you could otherwise think that B goes after a and that's not the case here.

I also found the same thing. I think that there is an error in the question?