@Test
public void testCommitOffsetOnly() {

    subscriptions.assignFromUser(Arrays.asList(tp));
    client.prepareResponse(consumerMetadataResponse(node, Errors.NONE.code()));
    coordinator.ensureCoordinatorReady();
    client.prepareResponse(offsetCommitResponse(Collections.singletonMap(tp, Errors.NONE.code())));
    AtomicBoolean success = new AtomicBoolean(false);
    coordinator.commitOffsetsAsync(Collections.singletonMap(tp, new OffsetAndMetadata(100L)), callback(success));
    assertTrue(success.get());
    assertEquals(100L, subscriptions.committed(tp).offset());
}