的競爭條件

Question

單元測試考慮代碼：

class TestClass 
{ 
    private bool _someFlag; 
    private object _sharedObject = new object(); 
    private readonly object _syncObject = new object(); 

    public object Read() 
    { 
     //lock (_syncObject) 
     { 
      _someFlag = false; 
      return _sharedObject; 
     } 
    } 

    public void Write(object obj) 
    { 
     //lock (_syncObject) 
     { 
      _someFlag = true; 
      _sharedObject = obj; 
     } 
    } 
} 

它有競爭狀態的問題。當我們撥打Read()某些線程可以撥打_someFlag = false;和return _sharedObject;行之間的Write()行。我要通過lock運營商修復問題。但是請你幫我單元測試一下這個競賽狀態問題。

我不想將_someFlag更改爲public用於測試目的或類似的東西。 我想要做這樣的事情：

[Fact] 
public void RaceConditionTest() 
{ 
    var correctObject = new object(); 
    var test = new TestClass(); 

    for (int i = 0; i < 1000; i++) 
    { 
     test.Write(correctObject); 
     var assertTask = Task.Run(() => 
     { 
      var actualObj = test.Read(); 
      Assert.True(object.ReferenceEquals(correctObject, actualObj), $"Failed on {i} iteration"); 
     }); 
     //Thread.Sleep(50); 
     var failTask = Task.Run(() => test.Write(new object())); 

     Task.WaitAll(assertTask, failTask); 
    } 
} 

但我怎麼能確定assertTask將failTask之前啓動？或者，也許有另一種方法來單元測試這種情況？提前致謝。

Answer 1

我住這種方法。但仍然在尋找更好的方法... 此測試在某些迭代中失敗，但如果您取消註釋lock運算符，測試將通過。

class TestClass 
{ 
    private IEventRecorder _eventRecorder; 


    private bool _someFlag; 
    private object _sharedObject = new object(); 
    private readonly object _syncObject = new object(); 

#if DEBUG 
    public void SetEventRecorder(IEventRecorder eventRecorder) => _eventRecorder = eventRecorder; 
#endif 

    public object Read() 
    { 
     //lock (_syncObject) 
     { 
#if DEBUG 
      _eventRecorder?.Record(nameof(Read)); 
#endif 
      _someFlag = false; 
      return _sharedObject; 
     } 
    } 

    public void Write(object obj) 
    { 
     //lock (_syncObject) 
     { 
#if DEBUG 
      _eventRecorder?.Record(nameof(Write)); 
#endif 
      _someFlag = true; 
      _sharedObject = obj; 
     } 
    } 

    public interface IEventRecorder 
    { 
     void Record(string eventName); 
    } 
} 

public class TestClassTests 
{ 
    private class EventRecorder : TestClass.IEventRecorder 
    { 
     private string _events = string.Empty; 

     public void Record(string eventName) => _events += eventName; 

     public string Events => _events; 

     public void Reset() => _events = string.Empty; 
    } 

    [Fact] 
    public void RaceConditionTest() 
    { 
     var correctObject = new object(); 
     var eventRecorder = new EventRecorder(); 
     var test = new TestClass(); 
     test.SetEventRecorder(eventRecorder); 

     for (int i = 0; i < 1000; i++) 
     { 
      test.Write(correctObject); 
      var assertTask = Task.Run(() => 
      { 
       var actualObj = test.Read(); 
       if (eventRecorder.Events.StartsWith("WriteRead")) 
        Assert.True(object.ReferenceEquals(correctObject, actualObj), $"Failed on {i} iteration"); 
      }); 
      var failTask = Task.Run(() => test.Write(new object())); 

      Task.WaitAll(assertTask, failTask); 
      eventRecorder.Reset(); 
     } 
    } 
} 

Answer 2

你可以，如果assertTask正在運行或啓動failTask​​前完成檢查：

while (assertTask.Status != Running && assertTask.Status != RanToCompletion) 
Thread.Sleep(50);