anchor.diff:      #'diameter_base_answer-message'{'Result-Code' = ?INVALID_AVP_BITS}
           = call(Config, Req).
   
  +%% Send an accounting ACR that the server tries to answer with an
  +%% inappropriate header, resulting in no answer being sent and the
  +%% request timing out.
  +send_bad_answer(Config) ->
  +    Req = ['ACR', {'Accounting-Record-Type', ?EVENT_RECORD},
  +                  {'Accounting-Record-Number', 2}],
  +    {error, timeout} = call(Config, Req).
  +
   %% Send an ASR with an arbitrary AVP and expect success and the same
   %% AVP in the reply.
   send_arbitrary(Config) ->
  
positive.code: tc() ->
      [send_ok,
       send_nok,
       send_arbitrary,
       send_unknown,
       send_unknown_mandatory,
  
negative.code: 
  request(#diameter_base_accounting_ACR{'Session-Id' = SId,
                                        'Accounting-Record-Type' = RT,
                                        'Accounting-Record-Number' = 2 = RN},
          #diameter_caps{origin_host = {OH, _},
                         origin_realm = {OR, _}}) ->
      Ans = ['ACA', {'Result-Code', ?SUCCESS},
                    {'Session-Id', SId},
                    {'Origin-Host', OH},
                    {'Origin-Realm', OR},
                    {'Accounting-Record-Type', RT},
                    {'Accounting-Record-Number', RN}],
  
      {reply, #diameter_packet{header = #diameter_header{is_error = true},%% not
                               msg = Ans}};
  
  request(#diameter_base_accounting_ACR{'Session-Id' = SId,
                                        'Accounting-Record-Type' = RT,
                                        'Accounting-Record-Number' = RN},
          #diameter_caps{origin_host = {OH, _},
                         origin_realm = {OR, _}}) ->
  