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.

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.