public ConcurrentMap<String, ConcurrentMap<Integer, Long>> getOffsetTable() {
        return offsetTable;
    }
@Test
    public void testOffsetPersistInMemory() {
        ConcurrentMap<String, ConcurrentMap<Integer, Long>> offsetTable = consumerOffsetManager.getOffsetTable();
        ConcurrentMap<Integer, Long> table = new ConcurrentHashMap<>();
        table.put(0, 1L);
        table.put(1, 3L);
        String group = "G1";
        offsetTable.put(group, table);

        consumerOffsetManager.persist();
        ConsumerOffsetManager manager = new ConsumerOffsetManager(brokerController);
        manager.load();

        ConcurrentMap<Integer, Long> offsetTableLoaded = manager.getOffsetTable().get(group);
        Assert.assertEquals(table, offsetTableLoaded);
    }