anchor.diff:              application:stop(amoc)
       end.
   
  --spec start_users(amoc:scenario(), [amoc_scenario:user_id()], state()) ->
  -    [term()].
  -start_users(Scenario, UserIds, State) ->
  -    [ start_user(Scenario, Id, State) || Id <- UserIds ].
  -
  --spec start_user(amoc:scenario(), amoc_scenario:user_id(), state()) ->
  -    supervisor:startchild_ret().
  -start_user(Scenario, Id, State) ->
  +-spec start_users(amoc:scenario(), [amoc_scenario:user_id()], non_neg_integer(),
  +                  state()) -> [term()].
  +start_users(Scenario, UserIds, Interarrival, State) ->
  +    [ start_user(Scenario, Id, Interarrival, State) || Id <- UserIds ].
  +
  +-spec start_user(amoc:scenario(), amoc_scenario:user_id(), non_neg_integer(),
  +                 state()) -> supervisor:startchild_ret().
  +start_user(Scenario, Id, Interarrival, State) ->
       R = supervisor:start_child(amoc_users_sup, [Scenario, Id, State]),
  -    timer:sleep(interarrival()),
  +    timer:sleep(Interarrival),
       R.
   
   -spec stop_users([amoc_scenario:user_id()], boolean()) -> [true | stop].
  
positive.code: 
  -spec handle_cast(any(), state()) -> {noreply, state()}.
  handle_cast({add, Count}, State) ->
      handle_add(Count, State),
      {noreply, State};
  handle_cast({remove, Count, Opts}, State) ->
      handle_remove(Count, Opts, State),
  
negative.code:          do/7,
           add/1,
           add/2,
           add/3,
           remove/1,
           remove/2,
           remove/3,
  