protected abstract Iterator<C> containerIterator(int partitionId);
@Test
    public void testEmptyIterator() {
        TestContainerCollector collector = new TestContainerCollector(nodeEngine, false, false);
        Iterator<Object> iterator = collector.containerIterator(0);

        assertInstanceOf(AbstractContainerCollector.EmptyIterator.class, iterator);
        assertFalse("Expected no next elements in iterator", iterator.hasNext());
        try {
            iterator.next();
            fail("Expected EmptyIterator.next() to throw NoSuchElementException");
        } catch (NoSuchElementException expected) {
            ignore(expected);
        }
        try {
            iterator.remove();
            fail("Expected EmptyIterator.remove() to throw UnsupportedOperationException");
        } catch (UnsupportedOperationException expected) {
            ignore(expected);
        }
    }