We can criticize the solutions, but actually the problem is with the Kata: there are no test cases for the negative case. Yes, it's easy to slip through on this, but that's why the tests should cover all cases, not just the happy ones.

That is where everybody goes wrong, but you are right

After pondering your reply and playing around in python with this, I realize my less-than-elegant solution would fail too. Thanks for bringing this up! It's the kind of gotcha that can slip through a simple reading. Duly noted!