In your IDE you cannot test the whole bunch of tests, which include random tests. Don't be disappointed, this is very common, and the work you have done was probably not in vain, it just probably means it needs some extra adjustments. You should try to debug your solution understanding the cases where it fails. If you feel helpless (and even if you don't), you may find some helpful tips in the official documentation: https://docs.codewars.com/training/troubleshooting/

Hi. It's not clear what's the problem you are trying to point out here. Could you be more explicit please? Maybe start reading there: https://docs.codewars.com/getting-started/solving-kata

I tried your code on sample tests and it gives things like that:

expected [ [ 1, 2, 3 ],
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined,
  undefined ] to deeply equal [ [ 1, 2, 3 ] ]

Which means your code return the first array (array with several undefineds while it should have returned the second one [[1,2,3]]). This is a good starting point to try debugging your code.