If you want to include testing for default arguments, or optional arguments, that's fine; but in that case it might be a good idea to mention this in the instructions...

Below you mean. Whoops, closed on accident. Author has to approve it.

I can't change main idea. Only translate. Probably this test show your understanding default arguments.

What is the point of this test: test.assert_equals(arr(), []) ??????

Gotcha, thanks!

Not exactly... when python creates a list (or string), it automatically saves its length. Finding the length is a single operation, not a loop through its elements. So no need to save it, and it's always O(1) complexity, no matter the length itself.

read more comments here:
https://stackoverflow.com/questions/699177/python-do-python-lists-keep-a-count-for-len-or-does-it-count-for-each-call

why not just assign the lengths of "l" and "d" to variables. This calculates the lengths of "d" and "l" 4 times.
I know the lengths of them are quite small in this kata, but still this doesn't seem efficient.

Oh man, that's way simpler than what I did.

Nailed it!

yep I guess I'm doing some basic mistake that I haven't figured out yet, but got some hints from you.. let me think about it a bit longer, problem must be on my side as no one else reporting this issue.. Thank you both, I'll confirm once solved :D.

You're probably not returning the recursive call to your function.

Solved?

Thank you for reply.
Nah, I have this inside my code..

    console.log(result);
    return result;

So it's returning as well..

You're supposed to return the stuff which you consider as your answer, you're logging them right now.

What am I doing wrong? When I console.log the result is correct, but the test response is undefined :-/. Thank you..

Time: 941ms Passed: 0 Failed: 4 Exit Code: 1
Test Results:
Basic tests
Log
[ 6, 7 ]
Expected: [6, 7], instead got: undefined
Log
[ 0, 1 ]
Expected: [0, 1], instead got: undefined
Log
[ 0, 1 ]
Expected: [0, 1], instead got: undefined
Log
[ 2, 2 ]
Expected: [2, 2], instead got: undefined
Completed in 5ms
STDERR
Unhandled rejection TestError: Expected: [6, 7], instead got: undefined