public Entry getPostingList(long key) {
        return dictionary.get(key);
    }
@Test
    void requireThatValuesCanBeInserted() {
        SimpleIndex.Builder builder = new SimpleIndex.Builder();
        builder.insert(KEY, new Posting(DOC_ID, 10));
        SimpleIndex index = builder.build();
        SimpleIndex.Entry e = index.getPostingList(KEY);
        assertNotNull(e);
        assertEquals(1, e.docIds.length);

        builder = new SimpleIndex.Builder();
        builder.insert(KEY, new Posting(DOC_ID, 10));
        builder.insert(KEY, new Posting(DOC_ID + 1, 20));
        index = builder.build();
        e = index.getPostingList(KEY);
        assertEquals(2, e.docIds.length);
        assertEquals(10, e.dataRefs[0]);
        assertEquals(20, e.dataRefs[1]);
    }