anchor.diff:                                 end,
                                  ok = Module:sync(C)
                          end,
  -              lists:foreach(Insert, [null | Values])
  -      end).
  -
  -compare(_Type, null, null) -> true;
  -compare(float4, V1, V2)    -> abs(V2 - V1) < 0.000001;
  -compare(float8, V1, V2)    -> abs(V2 - V1) < 0.000000000000001;
  -compare(hstore, {V1}, V2)  -> compare(hstore, V1, V2);
  -compare(hstore, V1, {V2})  -> compare(hstore, V1, V2);
  -compare(hstore, V1, V2)    ->
  +              lists:foreach(Insert, [null, undefined | Values])
  +      end).
  +
  +compare(_Type, null, null)      -> true;
  +compare(_Type, undefined, null) -> true;
  +compare(float4, V1, V2)         -> abs(V2 - V1) < 0.000001;
  +compare(float8, V1, V2)         -> abs(V2 - V1) < 0.000000000000001;
  +compare(hstore, {V1}, V2)       -> compare(hstore, V1, V2);
  +compare(hstore, V1, {V2})       -> compare(hstore, V1, V2);
  +compare(hstore, V1, V2)         ->
       orddict:from_list(format_hstore(V1)) =:= orddict:from_list(format_hstore(V2));
   compare(Type, V1 = {_, _, MS}, {D2, {H2, M2, S2}}) when Type == timestamp;
                                                           Type == timestamptz ->
  
positive.code:     check_type(Module, point, "'(23.15, 100)'", {23.15, 100.0}, []).
  
  geometry_type_test(Module) ->
      check_type(Module, geometry, "'COMPOUNDCURVE(CIRCULARSTRING(0 0,1 1,1 0),(1 0,0 1))'", 
        {compound_curve,'2d',
            [{circular_string,'2d',
                [{point,'2d',0.0,0.0,undefined,undefined},
  
negative.code:     Values = [
          {[]},
          {[{null, null}]},
          {[{null, undefined}]}
          {[{1, null}]},
          {[{1.0, null}]},
          {[{1, undefined}]},
          {[{1.0, undefined}]},
          {[{<<"a">>, <<"c">>}, {<<"c">>, <<"d">>}]},
          {[{<<"a">>, <<"c">>}, {<<"c">>, null}]},
          {[{<<"a">>, <<"c">>}, {<<"c">>, undefined}]}
      ],
      check_type(Module, hstore, "''", {[]}, []),
      check_type(Module, hstore, "'a => 1, b => 2.0, c => null'",
  