Tests are wrong in this way, the sample tests use test.expect and that's no way to compare two arrays (try returning [1] or any non falsy value and it'll pass all sample tests).
What you've copied there won't work either (note that you're passing 3 arguments to your function).
The tests on attempt use another way that makes test.expect to work, there is a function that compares each element of the expected and actual array with each other.
test.assertDeepEquals should be used.

Sample tests != test suite. Your code is wrong.