Same bro xD.This was my first attempt seems I am getting a hang of it :)

Turns out i hit my head hard after i submitted - because i missed about the i flag :D

You can call the preloaded mystery function when you submit, just not from inside your solved function.

You aren't restricted on where you can use the Test codebase or what you put into the "Your Solution" window, though. Put your tests in that and just ignore the window for "Your Test Cases". Then don't forget to delete them before you finally submit, once you have a solution that passes.

The instructions specifically state that the function mystery() is available and we can 'play' with it to figure out what it does. Yet we are unable to call the function in either the testing area. We may only access it when clicking submit.

That means my super protection against cheating is working :)
I spent a lot of time to do this btw.

That would be true if I hadn't included this in the spec: "An empty array should return 0."