anchor.diff:                            observe_internal(0, Clock(), AccIn)
                         end,
                         Ewma,
  -                      [1,2,3,4,5,6,7,8,9,10]),
  +                      lists:seq(1, 10)),
     cost(#backend{ewma = Later}) =< Initial.
   
   initial_state() ->
  
positive.code: 
  precondition(_, _) -> true.
  
  postcondition(_S, {call,_,pick_backend,[Vips]}, Result) ->
    pick_backend_postcondition(Vips, Result);
  postcondition(_, _, _) -> true.
  
  
negative.code:                                                 clock = fun () -> Now end}
                                     end, [Higher, Lower]),
    %% We use inclusive bounds on both ends because large numbers
    %% (penalty is 1.0e307) will compare like this:
    %%    > 1.0e307 + 1 =:= 1.0e307.
    %%    true
    cost(BackendA) >= cost(BackendB).
  