In fact the array used in 2d test is the same as in first test. As you spliced array on first test then when 2d tests occurs array is modified.

( Description said :

Create a function named "rotate" that takes an array and returns a new one ...

It means (implicitly) array arguments should stay uncahnged.
Hope it helps.

Here's what I'm looking at. http://imgur.com/gallery/jVKsTmm/new

As you can see I didn't modify the array at all before logging it. It's not a huge deal, I can always just skip the kata, I just wanted to help out in case this is, in fact, a broken test.

Actually there's no test with [1,2,3,4] as argument. I'm afraid you've modified the array argument before logging it out.

I think I may have run into a bug in this kata. This is what I get for input and the subsequent failure message.

Arguments: [ 1, 2, 3, 4 ], 2
Expected: [4,5,1,2,3], instead got: [3,4,1,2]

How'd the array get bigger? Am I missing something obvious here? Or is this just a bad unit test?