You are correct - constablebrew. I have updated the tests with your suggestion and also updated the assumptions in the Kata description to make it explicit that input order of the array should not matter.

Hi OverZealous,
Thanks a lot for letting me know. I have fixed the typo and the example test cases should be working correctly now.

In this Kata the example test cases enumerated are -

Test.assertSimilar(twosDifference([1,2,3,4]),[[1,3][2,4]]);
Test.assertSimilar(twosDifference([1,3,4,6]),[[1,3],[4,6]]);

But when I try to run my solution against I get the following -
Test Failed: Expected: [null], instead got: [[1,3],[2,4]]

I am not able to see a test where the expected result is [null]. What am I missing ?
To make things more confusing if I submit my solution it passes all the tests...

I am the author of this Kata, but am new to authoring Kata's in Codewars. I am pretty sure I have not put any test cases where [null] is an expected result, but I might be wrong about that since this is my first Kata and there is a good chance I might have screwed up something.

Please let me know if this is the wrong place for this question...