anchor.diff:  
   prop_protobuffs_addressbook() ->
       ?FORALL({Addressbook},
  -	    {default(undefined,addressbook())},
  -	    begin
  -		Msg = {addressbook,Addressbook},
  -		addressbook_pb:decode_addressbook(addressbook_pb:encode_addressbook(Msg)),
  -		true
  +	    {default({addressbook,undefined},{addressbook,addressbook()})},
  +	    begin
  +		Decoded = addressbook_pb:decode_addressbook(addressbook_pb:encode_addressbook(Addressbook)),
  +		compare_messages(Addressbook,Decoded)
   	    end).
   
   repeater_location() ->
  
positive.code:     {outer_middlebb,default(undefined,Inner)}.
  
  prop_protobuffs_nested2() ->
      ?FORALL({MiddleAA, MiddleBB},
  	    {default(undefined,middleAA()),default(undefined,middleBB())},
  	    begin
  		Msg = {outer,MiddleAA,MiddleBB},
  		Msg == nested2_pb:decode_outer(nested2_pb:encode_outer(Msg))
  	    end).
  
  inner() ->
  
negative.code: 
  prop_protobuffs_nested5_1() ->
      ?FORALL({Inner},
  	    {default({first,undefined},{first,first_inner()})},
  	    begin
  		Decoded = nested5_pb:decode_first(nested5_pb:encode_first(Inner)),
  		compare_messages(Inner,Decoded)
  	    end).
  
  prop_protobuffs_nested5_2() ->
      ?FORALL({Inner},
  	    {{second,first_inner()}},
  	    begin
  		Decoded = nested5_pb:decode_second(nested5_pb:encode_second(Inner)),
  		compare_messages(Inner,Decoded)
  	    end).
  
  enum_value() ->
  