The changes to the implementation requirements for the reversed() methods of Deque, List, SortedMap, and SortedSet contain some wording that appears to be a testable assertion. For example, the Deque.reversed() implementation requirements state:

    The exact relationship between calls on the view and calls on this
    Deque is unspecified. However, order-sensitive operations generally
    delegate to the appropriate method with the opposite orientation. For
    example, calling {@code getFirst} on the view results in a call to
    {@code getLast} on this Deque.

(List, SortedMap, and SortedSet contain similar wording, with changes corresponding to the interface name.)

The intent was not that this be a testable assertion, but rather that this serve as an example of the kinds of behavior that clients of the interfaces can expect.