@Override
    public ConsumerBuilder<T> maxAcknowledgmentGroupSize(int messageNum) {
        checkArgument(messageNum > 0, "acknowledgementsGroupSize needs to be > 0");
        conf.setMaxAcknowledgmentGroupSize(messageNum);
        return this;
    }
@Test
    public void testMaxAcknowledgmentGroupSizeInvalid() {
        try {
            consumerBuilderImpl.maxAcknowledgmentGroupSize(0);
            fail("Should throw exception");
        } catch (IllegalArgumentException e) {
            // expect exception
            assertEquals(e.getMessage(), "acknowledgementsGroupSize needs to be > 0");
        }
    }