anchor.diff:  
   Future testing_helper(Future f,String name){
     print("start  $name");
  -  return f.then((_)=>print("PASSED $name"),onError: (e)=>print("ERROR $name => $e"));
  +  return f.then((_)=>print("PASSED $name"),onError: (e){print("ERROR $name => $e"); throw(e);});
   }
   
   main(){
  
positive.code: import 'dart:async';
  import 'dart:collection';
  import 'dart:convert';
  import '../lib/redis.dart';
  
  part 'testcas.dart';
  
negative.code:   .then((_)=>testing_performance(test_pubsub_performance,"pubsub performance",20000))
    .then((_){
      //just increase this number if you have more time (I did, but I lost paitence)
      return testing_helper(test_long_running(20000),"one by one for longer time");
    })
    .then((_){
      return testing_performance(test_performance,"raw performance",200000);
    })
    .then((_){
      print("all tests PASSED!");
      exit(0);
    })
    .catchError((e){
      print("some of tests FAILED! $e");
      exit(-1);
    });
  }
  
  