The rot13 just means an alphabet with 13 letters in it. This test tests your code for the following note in the description:

-The function must work for any arbitrary alphabets, not only the pre-defined ones.

I had the same problem. You need to round up the result.

Remember, the list can be empty.

I have noticed that the description does not specify how many parts of string do we need to return for cases when we have a very short string (for example with only 3 characters).
In above case, my code returned only 3 parts and all tests passed. Maybe the rule should be to always return 5 parts with unused parts containing empty string.

It doesn't seem to be resolved. I had to return array with element 0 for n=0 to make the tests pass.

Your test case has Assert with wrong order. It has actual first, then expected.