anchor.diff:  
   process(f, 'to', Addr) when is_record(Addr, sip_hdr_address) ->
       format_address(Addr);
  -
  -%% ...
  -
  -
  -%% ...
  -process(pn, <<"k">>, _Ignore) -> 'supported';
  -process(fn, 'supported', _Ignore) -> <<"Supported">>;
  -process(p, 'supported', Bin) ->
  -    {ExtBin, Rest} = sip_binary:parse_token(Bin),
  -    Ext = sip_binary:binary_to_existing_atom(sip_binary:to_lower(ExtBin)),
  -    parse_list('supported', Ext, Rest);
  -
  -process(f, 'supported', Ext) ->
  -    sip_binary:any_to_binary(Ext);
   
   %% ...
   process(fn, 'unsupported', _Ignore) -> <<"Unsupported">>;
  
positive.code:      % Server
       ?_assertEqual(<<"HomeServer v2">>, parse('server', <<"HomeServer v2">>)),
       ?_assertEqual(<<"HomeServer v2">>, format('server', <<"HomeServer v2">>)),
       
       % Subject
       ?_assertEqual(<<"Need more boxes">>, parse('subject', <<"Need more boxes">>)),
       ?_assertEqual(<<"Need more boxes">>, format('subject', <<"Need more boxes">>)),
       
  
       % To
       ?_assertEqual(address(<<"Bob Zert">>, <<"sip:bob@biloxi.com">>, [{'tag', <<"1928301774">>}]),
  
negative.code:      ?_assertEqual([foo, bar], parse('require', <<"foo, bar">>)),
       ?_assertEqual(<<"foo, bar">>, format('require', [foo, bar])),
  
       ?_assertEqual([foo, bar], parse('unsupported', <<"foo, bar">>)),
       ?_assertEqual(<<"foo, bar">>, format('unsupported', [foo, bar])),
  
  