anchor.diff:  
   -spec lookup_chunk_server(torrent_id()) -> pid().
   lookup_chunk_server(TorrentID) ->
  -    gproc:where({n, l, chunk_server_key(TorrentID)}).
  +    gproc:lookup_pid({n, l, chunk_server_key(TorrentID)}).
   
   chunk_server_key(TorrentID) ->
       {etorrent, TorrentID, chunk_server}.
  
positive.code: lookup_registered_case() ->
      ?assertEqual(true, ?chunk_server:register_chunk_server(0)),
      ?assertEqual(self(), ?chunk_server:lookup_chunk_server(0)).
  
  not_interested_case() ->
      Srv = initial_chunk_server(1),
  
negative.code:         fun()  -> application:start(gproc) end,
          fun(_) -> application:stop(gproc) end,
          [?_test(lookup_registered_case()),
           ?_test(unregister_case()),
           ?_test(not_interested_case()),
           ?_test(request_one_case())
          ]}.
  