@Nullable
    @Override
    public RecordAndPosition<E> next() {
        final RecordAndPosition<E> next = this.element;
        this.element = null;
        return next;
    }
@Test
    void testEmptyConstruction() {
        final SingletonResultIterator<Object> iter = new SingletonResultIterator<>();
        assertThat(iter.next()).isNull();
    }