That's fair, thanks. Whenever I start looking at bit-level stuff I start wanting to make sure it's rock solid, a habit drilled into me from my professors.

It's 7 kyu kata, I don't think there's a need to make it more complicated than it already is

Yes, I don't make suggestions or comments on katas often.
Since the function allows input of two 64 bit numbers, good practice is to be prepared for a result that may be longer than the inputs.
There is a test for adding two zeroes; there should be a test for the upper bounds as well, in my opinion.

Is this a question? The short answer is probably "no".

The long answer is that tests are specifically written to avoid 64 bit overflow, so the answer is probably "no".

In C++, since input is uint64_t, should tests include edge case for result that is 65 bits long, e.g. add_binary(UINT64_MAX + UINT64_MAX)?

can you give me soluttion

Okay but what is the question?

You should remember that when adding in decimal and adding in binary, you get the same number. (For example 3(10) = 11(2))

And for people who write in JS, the toString method will also help.

The edge case is 0 + 0

should_handle_edge_case fails
Can I know what are the edge cases?

Approved

Lua translation!