@Override
    public ListenableFuture<?> spill(Iterator<Page> pageIterator)
    {
        requireNonNull(pageIterator, "pageIterator is null");
        checkNoSpillInProgress();
        spillInProgress = executor.submit(() -> writePages(pageIterator));
        return spillInProgress;
    }
@Test
    public void testSpill()
            throws Exception
    {
        assertSpill(false, false);
    }