anchor.diff:          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())
           ]}.
  
positive.code: 
  -spec lookup_chunk_server(torrent_id()) -> pid().
  lookup_chunk_server(TorrentID) ->
      gproc:where({n, l, chunk_server_key(TorrentID)}).
  
  chunk_server_key(TorrentID) ->
      {etorrent, TorrentID, chunk_server}.
  
negative.code: lookup_registered_case() ->
      ?assertEqual(true, ?chunk_server:register_chunk_server(0)),
      ?assertEqual(self(), ?chunk_server:lookup_chunk_server(0)).
  
  unregister_case() ->
      ?assertEqual(true, ?chunk_server:register_chunk_server(3)),
      ?assertEqual(true, ?chunk_server:unregister_chunk_server(3)),
      ?assertError(badarg, ?chunk_server:lookup_chunk_server(3)).
  
  not_interested_case() ->
      Srv = initial_chunk_server(1),
  