public Item and(Item item) {
        Item result = and(getRoot(), item);
        setRoot(result);
        return result;
    }
@Test
    void addNotToNot() {
        NotItem not1 = new NotItem();
        not1.addPositiveItem(new WordItem("p1"));
        not1.addNegativeItem(new WordItem("n1.1"));
        not1.addNegativeItem(new WordItem("n1.2"));

        NotItem not2 = new NotItem();
        not2.addPositiveItem(new WordItem("p2"));
        not2.addNegativeItem(new WordItem("n2.1"));
        not2.addNegativeItem(new WordItem("n2.2"));

        QueryTree tree = new QueryTree(not1);
        tree.and(not2);

        assertEquals("+(AND p1 p2) -n1.1 -n1.2 -n2.1 -n2.2", tree.toString());
    }