I fixed the failure message for the example test. I think that solves this. Closing.

Test.assert_equals(items.contains_all?([9,2,5,4,10]), false, 'items.contains_all?([9,2,5,4,10] should have been true')

The test expects false, so the error message is wrong. Are you sure items array is the same in both tests? Are you mutating the array?

No. "44421" should return "0" as stated by the rules.