@Override
    public long next() {
        return forceNext();
    }
@Test
    public void testNext() {
        // regular operation
        next(new DummyOperation());
        next(new DummyOperation());

        // backup-aware operation
        next(new DummyBackupAwareOperation());
        next(new DummyBackupAwareOperation());

        //urgent operation
        next(new DummyPriorityOperation());
        next(new DummyPriorityOperation());
    }