anchor.diff:  
   % logger:add_handler/3, OTP-21
   has_logger_add_handler_3() ->
  -    code:ensure_loaded(logger),
  +    _ = code:ensure_loaded(logger),
       erlang:function_exported(logger, add_handler, 3).
   
   test_has_logger_add_handler_3(_Config) ->
  
positive.code: 
  % maps:take/2, OTP-19
  has_maps_take_2() ->
      code:ensure_loaded(maps),
      erlang:function_exported(maps, take, 2).
  
  test_has_maps_take_2(_Config) ->
  
negative.code: 
  % cerl_sets:new/0, OTP-18
  has_cerl_sets_new_0() ->
      _ = code:ensure_loaded(cerl_sets),
      erlang:function_exported(cerl_sets, new, 0).
  
  test_has_cerl_sets_new_0(_Config) ->
  