anchor.diff:      DateTime start = new DateTime.now();
       for (var i = 0; i < times; i++) {
         prepareData();
  -      if (times == 1) {
  -        print('Before sort:');
  -        print(this);
  -      }
  +      sortFn(dataStore, swap);
  +    }
   
  -      sortFn(dataStore, swap);
  -
  -      if (times == 1) {
  -        print('After sort:');
  -        print(this);
  -      }
  -    }
  -    if (times > 1) {
  -      var costTime = new DateTime.now().difference(start).inMilliseconds;
  -      print('$times times cost: $costTime ms');
  -    }
  +    var costTime = new DateTime.now().difference(start).inMilliseconds;
  +    print('${dataStore.length} items costs : $costTime ms');
     }
   
     clear() {
  
positive.code:     arr[index2] = temp;
    }
  
    String toString() {
      return dataStore.toString();
    }
  
negative.code: import 'package:test/test.dart';
  
  class TestBed {
    List<int> dataStore;
    int length;
    int times;
    Function sortFn;
    bool auto;
  
    TestBed(this.length, this.sortFn, {this.auto = false, this.times = 1}) {
      if (auto) {
        sort();
      }
  