Week 2 Question 2 - Test doesn't check that original array was not modified

[laky]

The requirements state that the original array should not be changed, however the tests do not check that. It would be good to add this check into the tests below.

https://github.com/CodeYourFuture/js-exercises/blob/master/week-2/Homework/mandatory/2-function-creation.js#L92-L106