anchor.diff:  
   -spec seeder(boolean(), peerstate()) -> peerstate().
   seeder(Status, Peerstate) ->
  -    #peerstate{seeder=Current} = Peerstate,
       Status orelse erlang:error(badarg),
       Peerstate#peerstate{seeder=Status}.
   
  
positive.code:      ?_assertNot(?state:seeding(?state:hasnone(S0))),
       ?_assertNot(?state:seeding(?state:hasone(0, S0)))].
  
  -endif.
  
  
negative.code:     [?_assert(?state:choked(State)),
       ?_assertNot(?state:interested(State)),
       ?_assertNot(?state:seeder(State)),
       ?_assertEqual(0, ?rqueue:size(?state:requests(State))),
       ?_assertNot(?state:needreqs(State)),
       ?_assertError(badarg, ?state:pieces(State)),
       ?_assertError(badarg, ?state:interesting(0, State))].
  
  