anchor.diff:  
   %% @doc
   %% @end
  --spec valid(non_neg_integer(), pid()) -> ok.
  +-spec valid(pieceindex(), pid()) -> ok.
   valid(Piece, Srvpid) ->
       Srvpid ! {piece, {valid, Piece}},
       ok.
  
positive.code: %% This module provides a common interface for processes
  %% handling piece state changes.
  
  -export([stored/2,
           valid/2]).
  
  %% @doc
  %% @end
  -spec stored(non_neg_integer(), pid()) -> ok.
  stored(Piece, Srvpid) ->
      Srvpid ! {piece, {stored, Piece}},
      ok.
  
negative.code: -ifdef(TEST).
  -include_lib("eunit/include/eunit.hrl").
  -define(piecestate, ?MODULE).
  
  begun_test() ->
      ?assertEqual(ok, ?piecestate:begun(0, self())),
      ?assertEqual({piece, {begun, 0}}, etorrent_utils:first()).
  
  stored_test() ->
      ?assertEqual(ok, ?piecestate:stored(0, self())),
  