anchor.diff:      {error, ttl_expired} = aetx:check(RTx6, Trees2, CurrHeight2, ?PROTOCOL_VERSION),
       ok.
   
  +extend_oracle_negative_dynamic_fee(Cfg) ->
  +    {OracleKey, S2} = register_oracle(Cfg),
  +    Trees2          = aeo_test_utils:trees(S2),
  +    CurrHeight2     = ?ORACLE_EXT_HEIGHT,
  +
  +    F = fun(ExtTxOpts) -> aetx:check(aeo_test_utils:extend_tx(OracleKey, ExtTxOpts, S2), Trees2, CurrHeight2, ?PROTOCOL_VERSION) end,
  +    1 = MinFee = aec_governance:minimum_tx_fee(),
  +
  +    %% Test minimum fee for increasing TTL.
  +    ?assertEqual({error, too_low_fee}, F(#{oracle_ttl => {delta, 0}, fee => 0})),
  +    ?assertMatch({ok, _}             , F(#{oracle_ttl => {delta, 0}, fee => MinFee})),
  +    ?assertEqual({error, too_low_fee}, F(#{oracle_ttl => {delta, 1}, fee => MinFee})),
  +    ?assertMatch({ok, _}             , F(#{oracle_ttl => {delta, 1}, fee => 1 + MinFee})),
  +    ?assertMatch({ok, _}             , F(#{oracle_ttl => {delta, 999}, fee => 1 + MinFee})),
  +    ?assertMatch({ok, _}             , F(#{oracle_ttl => {delta, 1000}, fee => 1 + MinFee})),
  +    ?assertEqual({error, too_low_fee}, F(#{oracle_ttl => {delta, 1001}, fee => 1 + MinFee})),
  +    ?assertMatch({ok, _}             , F(#{oracle_ttl => {delta, 1001}, fee => 2 + MinFee})),
  +    %% Test more than minimum fee considering TTL.
  +    ?assertMatch({ok, _}             , F(#{oracle_ttl => {delta, 1001}, fee => 3 + MinFee})),
  +    ok.
  +
   extend_oracle(Cfg) ->
       {OracleKey, S} = register_oracle(Cfg),
       PrivKey        = aeo_test_utils:priv_key(OracleKey, S),
  
positive.code:     {error, ttl_expired} = aetx:check(RTx5, Trees, 2, ?PROTOCOL_VERSION),
      ok.
  
  register_oracle(_Cfg) ->
      {PubKey, S1} = aeo_test_utils:setup_new_account(aeo_test_utils:new_state()),
      Tx           = aeo_test_utils:register_tx(PubKey, S1),
      PrivKey      = aeo_test_utils:priv_key(PubKey, S1),
  
      %% Test that RegisterTX is accepted
  
negative.code: %% test case exports
  -export([ extend_oracle/1
          , extend_oracle_negative/1
          , extend_oracle_negative_dynamic_fee/1
          , prune_oracle/1
          , prune_oracle_extend/1
          , prune_query/1
  