Mixing up the two arguments is not funny.

Array [0,1,2]
Param 0

Expected: '[0, 1, 2]', instead got: '[0, 1, 2, 0]'

Is this correct?

I passed the other tests except this one.

Instructions aren't very clear. Also, sometimes param and arr seem to be mixed up (e.g. param is an array instead of arr). If this is expected, it would be helpful if were spelled out in the instructions. Otherwise, this was a good kata.

You should consider to add random test.