anchor.diff:  	    log:log("~n"),
   	    interleave(Mod, Fun, Args);
   	error ->
  -	    error
  +	    ?RET_INSTR_ERROR
       end.
   
   %% Produce all possible process interleavings of (Mod, Fun, Args).
  --spec interleave(atom(), atom(), [any()]) -> 'true'.
  +-spec interleave(atom(), atom(), [any()]) -> ?RET_NORMAL | ?RET_HEISENBUG.
   
   interleave(Mod, Fun, Args) ->
       register(sched, self()),
  
positive.code: 		 {Val3, Set3} = set_pop(Set2),
  		 List2 = lists:sort([Val1, Val2, Val3]),
  		 ?assertEqual(List1, List2),
  		 ?assert(set_is_empty(Set3))
  	     end)}].
  
  -spec lid_test_() -> any().
  
negative.code: %%%----------------------------------------------------------------------
  
  %% Instrument file Path and produce all interleavings of (Mod, Fun, Args).
  -spec analyze(string(), atom(), atom(), [any()]) -> ?RET_NORMAL |
  						    ?RET_HEISENBUG |
  						    ?RET_INSTR_ERROR.
  
  analyze(File, Mod, Fun, Args) ->
      case instr:instrument_and_load(File) of
  