Hey, I had issues with that case at first as well, but remember the structure of the variables does not depend on any strings or integers within them. i.e ['[','s'] has the same structure as [1,2] if I am not mistaken. So the data types within the list actually do not matter, what does matter is the structure, i.e [] of the list. That case is used to invalidate string conversions of the entire list.

Fixed ruby tests to include only valid values.

Well, 8k is syntax knowledge and 7k is language api knowledge. Seems more like a 6kyu kata for me. But yeah we can agree on fact that 5k is overrated.

They probably marked it up in difficulty because there are no "run test" test cases at least for the ruby translation, but I agree with you. I think run test test cases should be added and this should moved to 7 or 8