Thanks for your feedback. I've taken them into consideration, and even started to edit the Kata accordingly, but soon found myself being redundant.

1. The requirements on the input are clearely stated as "non-negative integer". "Valid" means that the input complies with the requirements specified. There is nothing to add. Non-negative integer means n >= 0, so adding that is redundant.
2. I made a change to specify the bytes are represented by a string of '0' and '1' of length 8.
3. Examples are given by the exmaple test cases. To repeat the test cases is redundant. A code warrior should be able to code to test cases. That's part of a programmers job and part of this kata's challenge. Suggest a higher kyu if you think this adds to the difficulty.
4. I chose to add a random test. If anything in the description was not clear, this test case provides the necessary details. The test case does not provide the solution; it only validates the solution once found.

I'm marking this issue as resolved.

There are a couple random string tests implemented, not names though, that would be much harder :)

I fixed it! The function should return None when given an empty string, or a string less than length 2.

Really?! What part is ambiguous or not clear? What exactly did you misunderstand? Do you have any suggestions for better text?