If the number returned is greater than 4, then it's an error.

I send the number 0..=255 to 'quarter_of()' and receive the number 1..=4 in response, but there are only 12 months - can I make 'quarter_of()' notify about an error when receiving the number > 12 ?

Looks like the thing they found in Roswell...

When tests like "1234\n" fail, the output is unreadable. Showing $(repr(case)) should be better.
"\xbe" in the Python version corresponds to "¾". It's there to fail some solutions that check Unicode "numeric" property (IDK how anyone could come up with that solutions, but there was one), so it should better have 4 characters too, but I didn't update the Python version because republishing it is slow and buggy. So the test should be something like "9¾9¾".
IDK any details, but Base.rand is available and there are random tests n other katas in Julia.

I crafted a little translation to Julia.

In the first attempt unfortunately, I forgot to redact the full solution from the setup. I replaced it by a comment in the second commit. Also, please note that currently, as long as Julia is not updated to the latest version, random number generation is not available.