anchor.diff:  
   get_written_interval(L) ->
       ?LET({O, Ln}, elements(L), {O+1, Ln-1}).
  - 
  +
   %% INITIALIZATION
   
   -record(state, {pid, prev_extra = 0,
  +                filename = undefined,
                   planned_writes=[],
                   planned_trims=[],
                   written=[],
                   trimmed=[]}).
   
  -initial_state() -> #state{written=[{0,1024}]}.
  -initial_state(I, T) -> #state{written=[{0,1024}],
  -                              planned_writes=I,
  -                              planned_trims=T}.
  +-define(FILENAME, "machi_file_proxy_eqc_data").
  +
  +initial_state() ->
  +    %%#state{filename=undefined, written=[{0,1024}]}.
  +    {_, _, MS} = os:timestamp(),
  +    Filename = test_server:temp_name("eqc_data") ++ "." ++ integer_to_list(MS),
  +    %% Filename = ?FILENAME,
  +    #state{filename=Filename, written=[{0,1024}]}.
  +
  +initial_state(I, T) ->
  +    S=initial_state(),
  +    S#state{written=[{0,1024}],
  +            planned_writes=I,
  +            planned_trims=T}.
   
   weight(_S, rewrite) -> 1;
   weight(_S, _) -> 2.
  
positive.code:             true;
          {error, not_written} when Chopped =:= [] andalso Trimmed =:= [] ->
              true;
          Other ->
              ?debugVal(Other),
              is_error(Res)
      end.
  
  
negative.code:     L1 = lists:map(fun({Pos, Sz}) -> Pos + Sz end, L0),
      lists:last(lists:sort(L1)).
  
  cleanup() ->
      [begin
           Fs = filelib:wildcard(?TESTDIR ++ Glob),
  