anchor.diff:    {_, _, Micro} = os:timestamp(),
     Micro rem Max.
   
  -start_subscriber(Config, Topics, InitArgs) ->
  +start_subscriber(GroupId, Config, Topics, InitArgs) ->
     %% use consumer managed offset commit behaviour by default, so we
     %% can control where to start fetching messages from
     DefaultGroupConfig = [ {offset_commit_policy, consumer_managed}
  
positive.code:        %% Send messages:
         {LastOffset, L} = produce_payloads(Topic, 0, Config),
         %% Start two subscribers competing for the partition:
         {ok, SubscriberPid1} = start_subscriber(Config, [Topic], InitArgs),
         {ok, SubscriberPid2} = start_subscriber(Config, [Topic], InitArgs),
         ?wait_message(_, _, _, LastOffset),
         L
       end,
  
negative.code:      #{ timeout => 5000 },
       %% Run stage:
       begin
         {ok, SubscriberPid} = start_subscriber(?group_id, Config, [Topic], InitArgs),
         %% Send a message to the topic and wait until it's received to make sure the subscriber is stable:
         produce({Topic, Partition}, <<0>>),
         {ok, _} = ?wait_message(Topic, Partition, <<0>>, _),
  