You must explicitly say about any rounding needed to complete tests ot kata itself.
I (and I guess not only me) am outraged that I am forced to play game "guess where there is rounding, and which one it is". And that it takes literally 20 times more time than finding an actual solution.

I had to look at kata discussion to find out what may be wrong.
And I found out that there actually was a discussion about empty array handling, but it was not finished.
In my opinion empty array looks like a pretty valid input, so the output should also be an empty array.
Right now I cant think of any reason why there should be 'array should contain only numbers'-output for an empty array. I mean empty array does not really contain anything that can be called 'not a number' since it does not contain, well, anything :)