anchor.diff:                 ?assertEqual({error, not_present},
                               ?TEST_MODULE:add_poi(accounts, AccountPubkey,
                                                    Trees0, Poi0))
  +       end},
  +      {"Empty PoI constructed from non-empty state trees can be serialized/deserialized",
  +       fun() ->
  +               AccountPubkey = <<123:?MINER_PUB_BYTES/unit:8>>,
  +
  +               Trees0 = aec_test_utils:create_state_tree(),
  +               Poi0 = ?TEST_MODULE:new_poi(Trees0),
  +
  +               Trees1 = ?TEST_MODULE:ensure_account(AccountPubkey, Trees0),
  +               Poi1 = ?TEST_MODULE:new_poi(Trees1),
  +
  +               assert_equal_poi(Poi1,
  +                                ?TEST_MODULE:deserialize_poi(
  +                                   ?TEST_MODULE:serialize_poi(Poi1))),
  +               ?assertNotEqual(?TEST_MODULE:serialize_poi(Poi0),
  +                               ?TEST_MODULE:serialize_poi(Poi1))
          end},
         {"POI for one account",
          fun() ->
  
positive.code:                ?assertEqual(?TEST_MODULE:hash(Trees0),
                              ?TEST_MODULE:poi_hash(Poi0))
         end},
        {"Non-empty PoI cannot be constructed from empty state trees",
         fun() ->
                 AccountPubkey = <<123:?MINER_PUB_BYTES/unit:8>>,
  
negative.code:                              ?TEST_MODULE:lookup_poi(accounts, Pubkey4, Poi4)),
  
                  %% Check serialization/deserialization of PoI
                  [assert_equal_poi(PoI,
                                    ?TEST_MODULE:deserialize_poi(
                                       ?TEST_MODULE:serialize_poi(PoI)))
                   || PoI <- [Poi1, Poi2, Poi2, Poi3, Poi4]]
          end
        }
      ].
  
  assert_equal_poi(PoIExpect, PoIExpr) ->
      %% The deserialized poi contains a gb_tree, so it is operation
      %% order dependent.  The serialized version is canonical, though.
      ?assertEqual(?TEST_MODULE:serialize_poi(PoIExpect),
                   ?TEST_MODULE:serialize_poi(PoIExpr)).
  