Ok. I am new to the site and this was the first kata where you had to write your own test cases. Now I see why I got the error message.

When I tried to test my solution, I got: "Failed to construct test fixture properly". Then I submitted the solution and it was accepted. Why is this? Is there something wrong with the kata or with the site? Or is it neccessary to write your own test cases?

Is it okay if you pass no arguments to funtion numbers(){ } and it returns true?

Seriously, in real-world applications you probably want to pick out NaN when you expect actual numbers. I threw in a check for NaN on my first pass and failed an attempt because of that.