the same here. I had this problem once with another kata and turned out I was printing the value instead of returing it. this time I can't find any mistake but I gueess the problem is on our end again ;)

Try your code with this test:

test.assert_equals(rot13(rot13("Test")),"Test")

I copied your code and run it in Codewars - you have a small error that should be easy for you to debug, since the error messages are very clear and you should notice the pattern in "why"/"where" your code is making the mistake.

The tests are ok. Your code not working is not a kata issue. Please read this and don't raise issues so lightly in the future: https://docs.codewars.com/training/troubleshooting/