Great Kata!
Just as a quick suggestion, you might want to add a capital letter in the example.
The description mentions capital letters as valid input, but never as valid hexidecimal characters so it wasn't immediately apparent to me that I should XOR them.
Description does not mention how to handle empty strings/strings with no hex characters.
(At least in Python this expects
0to be returned).Description doesn't mention that we have to convert hexadecimal characters into decimals first.
The initial code in Ruby is broken.
The function name should be in snake_case in Python and Ruby.
No random tests.
Great Kata!
Just as a quick suggestion, you might want to add a capital letter in the example.
The description mentions capital letters as valid input, but never as valid hexidecimal characters so it wasn't immediately apparent to me that I should XOR them.