Thanks, I'll give that a shot.

1. It's pretty clear that they means the numbers or special chars, not the whole string. Note it says the string not the strings.
2. The first value in the error message is what your function returned, so it's your function that's returning the wrong value there, print the input to check what it was and check your code to see why it does that.

1. The instructions are unclear. The instructions state: If there are numbers or special characters included in the string, they should be returned as they are. Only letters from the latin/english alphabet should be shifted, like in the original Rot13 "implementation".

First, it should explicity say what should be returned as they are...do you mean the string? or the character.

2. In some of the test cases how do 2 different non-alphanumeric characers with rot13 applied equal the same character? As in..
   'nopqrstuvwxy`abcdefghijklm' should equal 'nopqrstuvwxyzabcdefghijklm'
   'nopqrstuvwxyz{bcdefghijklm' should equal 'nopqrstuvwxyzabcdefghijklm'

'@Y3SEVEEEK37VH68' should equal 'ZY3SEVEEEK37VH68'
'@L3FRIRRRX37IU68' should equal 'ML3FRIRRRX37IU68'