anchor.diff:      {error,{not_found,h2}} = logger:remove_handler(h2),
   
       CallAddHandler = fun() -> logger:add_handler(h2,?MODULE,#{}) end,
  -    CrashHandler = fun() -> a = b end,
  +    CrashHandler = fun() -> erlang:error({badmatch,b}) end,
       KillHandler = fun() -> exit(self(), die) end,
   
       {error,{handler_not_added,{attempting_syncronous_call_to_self,_}}} =
  
positive.code:     {error,{not_found,h0}} = logger:remove_handler_filter(h0,hf),
      {error,{invalid_filter,_}} =
          logger:add_handler_filter(h1,hf,{fun(_) -> ok end,args}),
      ok = logger:add_handler_filter(h1,hf,{fun(_,_) -> a=b end,args}),
      {ok,#{filters:=[_]}} = logger:get_handler_config(h1),
      ok = logger:notice(M3=?map_rep),
      ok = check_logged(notice,M3,#{}),
  
negative.code:     %% Logger filters
      {error,{invalid_filter,_}} =
          logger:add_primary_filter(lf,{fun(_) -> ok end,args}),
      ok = logger:add_primary_filter(lf,
                                     {fun(_,_) ->
                                              erlang:error({badmatch,b})
                                      end,
                                      args}),
      #{filters:=[_]} = logger:get_primary_config(),
      ok = logger:notice(M1=?map_rep),
      ok = check_logged(notice,M1,#{}),
  