anchor.diff:      ok = gen_node:become(ChildId, double_fun()),
       ok = gen_node:reset(ChildId),
       #{state := ready} = gen_node:get_state(ChildId).
  +
  +gen_node_server_states(_) ->
  +    {ok, ChildId1, _ChildRef1} = gen_node:start_server(),
  +    {ok, ChildId2, _ChildRef2} = gen_node:start_server(),
  +    ok = gen_node:become(ChildId2, double_fun()),
  +    States = gen_node:get_states(),
  +    {ChildId1, #{state := ready}} = lists:keyfind(ChildId1, 1, States),
  +    {ChildId2, #{state := working}} = lists:keyfind(ChildId2, 1, States).
  
positive.code: %% Tests
  -export([gen_node_server_start/1]).
  -export([gen_node_server_state_after_start/1]).
  -export([gen_node_server_state_during_work/1]).
  -export([gen_node_server_work/1]).
  
  %% ============================================================================
  
negative.code:         gen_node_server_start,
          gen_node_server_state_after_start,
          gen_node_server_state_during_work,
          gen_node_server_work,
          gen_node_server_state_after_work,
          gen_node_server_states
      ].
  
  init_per_suite(Config) ->
  