There is no such test, you're confusing the logs, you returned [1,2,3,4] instead of None, print the input.

When you see in Python an error like this:

[1,2,3,4] should equal None

The first value is what your function wrongly returned, the second value is the expected one, to know the input value, you should print it and it'll appear above the test result, read this: https://docs.codewars.com/training/troubleshooting#print-input

For this case you must return [1, 2, 3, 5].