anchor.diff:      Diff = lists:subtract(Curr, Want),
       lists:usort(lists:subtract(Curr, Diff)).
   
  -do_notify(#state{node_renaming_txt_mref = MRef} = State) when MRef =/= undefined ->
  +do_notify(#state{node_renaming_txn_mref = MRef} = State) when MRef =/= undefined ->
       State;
   do_notify(#state{nodes = NodesOld} = State) ->
       NodesNew = do_nodes_actual_proper(),
  
positive.code: -record(state, {
            nodes :: [node()],
            we_were_shunned = false :: boolean(),
            node_renaming_txt_mref :: undefined | reference()
           }).
  
  -include_lib("eunit/include/eunit.hrl").
  
negative.code: 
  handle_call({register_node_renaming_txn, Pid}, _From, State) ->
      case State of
          #state{node_renaming_txn_mref = undefined} ->
              MRef = erlang:monitor(process, Pid),
              NewState = State#state{node_renaming_txn_mref = MRef},
              {reply, ok, NewState};
          _ ->
              {reply, already_doing_renaming, State}
  