anchor.diff:    brod_group_subscriber:stop(Pid3),
     ok.
   
  +t_assign_partitions_handles_updating_state({init, Config}) when is_list(Config) ->
  +  meck_subscribe_unsubscribe(),
  +  Config;
  +t_assign_partitions_handles_updating_state({'end', Config}) when is_list(Config) ->
  +  meck:unload(brod);
  +t_assign_partitions_handles_updating_state(Config) when is_list(Config) ->
  +  %% use consumer managed offset commit behaviour
  +  %% so we can control where to start fetching messages from
  +  GroupConfig = [ {offset_commit_policy, consumer_managed}
  +                , {partition_assignment_strategy, callback_implemented}
  +                ],
  +  ConsumerConfig = [ {prefetch_count, 10}
  +                   , {sleep_timeout, 0}
  +                   , {max_wait_time, 1000}
  +                   , {partition_restart_delay_seconds, 1}
  +                   ],
  +  CaseRef = t_assign_partitions_handles_updating_state,
  +  CasePid = self(),
  +  InitArgs = {CaseRef, CasePid, _IsAsyncAck = true, _IsAsyncCommit = false, _IsAssignPartitions = true},
  +  {ok, SubscriberPid} =
  +    brod:start_link_group_subscriber(?CLIENT_ID, ?GROUP_ID, [?TOPIC1],
  +                                     GroupConfig, ConsumerConfig,
  +                                     ?MODULE, InitArgs),
  +  ok = wait_for_subscribers([?TOPIC1], [SubscriberPid]),
  +  %% Since we only care about the assign_partitions part, we don't need to
  +  %% send and receive messages.
  +  ok = brod_group_subscriber:stop(SubscriberPid).
  +
  +
   %%%_* Help funtions ============================================================
   
   %% For test deterministc, we wait until all consumer group members are
  
positive.code:                    ],
    CaseRef = t_2_members_subscribe_to_different_topics,
    CasePid = self(),
    InitArgs = {CaseRef, CasePid, _IsAsyncAck = false, _IsAsyncCommit = false},
    {ok, SubscriberPid1} =
      brod:start_link_group_subscriber(?CLIENT_ID, ?GROUP_ID, [?TOPIC2],
                                       GroupConfig, ConsumerConfig,
  
negative.code:                    ],
    CaseRef = t_async_acks,
    CasePid = self(),
    InitArgs = {CaseRef, CasePid, _IsAsyncAck = true, _IsAsyncCommit = false, _IsAssignPartitions = false},
    Partition = 0,
    {ok, SubscriberPid} =
      brod:start_link_group_subscriber(?CLIENT_ID, ?GROUP_ID, [?TOPIC1],
  