在C#（按顺序）中引发事件的单元测试

我有一些引发

PropertyChanged

事件的代码，我希望能够单元测试事件是否正确引发

引发事件的代码如下

public class MyClass : INotifyPropertyChanged
{
   public event PropertyChangedEventHandler PropertyChanged;  

   protected void NotifyPropertyChanged(String info)
   {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
   }  

   public string MyProperty
   {
       set
       {
           if (_myProperty != value)
           {
               _myProperty = value;
               NotifyPropertyChanged("MyProperty");
           }
       }
   }
}

在我的单元测试中，我从以下代码中获得了一个不错的绿色测试，它使用委托：

[TestMethod]
public void Test_ThatMyEventIsRaised()
{
    string actual = null;
    MyClass myClass = new MyClass();

    myClass.PropertyChanged += delegate(object sender, PropertyChangedEventArgs e)
    {
         actual = e.PropertyName;
    };

    myClass.MyProperty = "testing";
    Assert.IsNotNull(actual);
    Assert.AreEqual("MyProperty", actual);
}

但是，如果我尝试将属性设置链接在一起，如下所示：

public string MyProperty
{
    set
    {
        if (_myProperty != value)
        {
            _myProperty = value;
            NotifyPropertyChanged("MyProperty");
            MyOtherProperty = "SomeValue";
        }
    }
}

public string MyOtherProperty
{
    set
    {
        if (_myOtherProperty != value)
        {
            _myOtherProperty = value;
            NotifyPropertyChanged("MyOtherProperty");
        }
    }
}

我对事件的测试失败-它捕获的事件是MyOtherProperty的事件

我很确定事件会触发，我的UI会像它一样做出反应，但我的委托只捕获最后一个要触发的事件

所以我想知道：
1.我测试事件的方法正确吗？

---

2.我提出连锁事件的方法正确吗

您所做的一切都是正确的，前提是您希望测试询问“最后引发的事件是什么？”

您的代码按以下顺序触发这两个事件

• 属性已更改（…“我的属性”…）
• 属性已更改（…“MyOtherProperty”…）

这是否“正确”取决于这些事件的目的

如果要测试引发的事件数量以及引发顺序，可以轻松扩展现有测试：

[TestMethod]
public void Test_ThatMyEventIsRaised()
{
    List<string> receivedEvents = new List<string>();
    MyClass myClass = new MyClass();

    myClass.PropertyChanged += delegate(object sender, PropertyChangedEventArgs e)
    {
        receivedEvents.Add(e.PropertyName);
    };

    myClass.MyProperty = "testing";
    Assert.AreEqual(2, receivedEvents.Count);
    Assert.AreEqual("MyProperty", receivedEvents[0]);
    Assert.AreEqual("MyOtherProperty", receivedEvents[1]);
}

[TestMethod]
公共无效性测试
{
List receivedEvents=新列表（）；
MyClass MyClass=新的MyClass（）；
myClass.PropertyChanged+=委托（对象发送方，PropertyChangedEventArgs e）
{
receivedEvents.Add（如PropertyName）；
};
myClass.MyProperty=“测试”；
aresequal（2，receivedEvents.Count）；
AreEqual（“MyProperty”，receivedEvents[0]）；
Assert.AreEqual（“MyOtherProperty”，receivedEvents[1]）；
}

如果您正在进行TDD，那么事件测试可以开始生成大量重复代码。我编写了一个事件监视器，它为这些情况下的单元测试编写提供了一种更干净的方法

var publisher = new PropertyChangedEventPublisher();

Action test = () =>
{
    publisher.X = 1;
    publisher.Y = 2;
};

var expectedSequence = new[] { "X", "Y" };

EventMonitor.Assert(test, publisher, expectedSequence);

更多详情请参见我对以下内容的回答

---

下面是一个稍加修改的Andrew代码，它不只是记录引发事件的序列，而是计算特定事件被调用的次数。虽然它是基于他的代码，但我发现它在我的测试中更有用

[TestMethod]
public void Test_ThatMyEventIsRaised()
{
    Dictionary<string, int> receivedEvents = new Dictionary<string, int>();
    MyClass myClass = new MyClass();

    myClass.PropertyChanged += delegate(object sender, PropertyChangedEventArgs e)
    {
        if (receivedEvents.ContainsKey(e.PropertyName))
            receivedEvents[e.PropertyName]++;
        else
            receivedEvents.Add(e.PropertyName, 1);
    };

    myClass.MyProperty = "testing";
    Assert.IsTrue(receivedEvents.ContainsKey("MyProperty"));
    Assert.AreEqual(1, receivedEvents["MyProperty"]);
    Assert.IsTrue(receivedEvents.ContainsKey("MyOtherProperty"));
    Assert.AreEqual(1, receivedEvents["MyOtherProperty"]);
}

[TestMethod]
公共无效性测试
{
Dictionary receivedEvents=新字典（）；
MyClass MyClass=新的MyClass（）；
myClass.PropertyChanged+=委托（对象发送方，PropertyChangedEventArgs e）
{
if（receivedEvents.ContainsKey（e.PropertyName））
receivedEvents[e.PropertyName]++；
其他的
receivedEvents.Add（如PropertyName，1）；
};
myClass.MyProperty=“测试”；
Assert.IsTrue（receivedEvents.ContainsKey（“我的财产”）；
aresequal（1，receivedEvents[“MyProperty”]）；
Assert.IsTrue（receivedEvents.ContainsKey（“MyOtherProperty”）；
Assert.AreEqual（1，receivedEvents[“MyOtherProperty”]）；
}

这是一个非常古老的版本，甚至可能不会被阅读，但通过一些很酷的新.net功能，我创建了一个INPC跟踪类，它允许：

[Test]
public void Test_Notify_Property_Changed_Fired()
{
    var p = new Project();

    var tracer = new INCPTracer();

    // One event
    tracer.With(p).CheckThat(() => p.Active = true).RaisedEvent(() => p.Active);

    // Two events in exact order
    tracer.With(p).CheckThat(() => p.Path = "test").RaisedEvent(() => p.Path).RaisedEvent(() => p.Active);
}

---

请参阅要点：

基于本文，我创建了这个简单的断言助手：

private void AssertPropertyChanged<T>(T instance, Action<T> actionPropertySetter, string expectedPropertyName) where T : INotifyPropertyChanged
    {
        string actual = null;
        instance.PropertyChanged += delegate (object sender, PropertyChangedEventArgs e)
        {
            actual = e.PropertyName;
        };
        actionPropertySetter.Invoke(instance);
        Assert.IsNotNull(actual);
        Assert.AreEqual(propertyName, actual);
    }

---

不要为每个成员编写测试-这是一项艰巨的工作

（也许这个解决方案并不适合所有情况，但它展示了一种可能的方法。您可能需要根据您的用例调整它）

可以使用库中的反射来测试您的成员是否都正确响应属性更改事件：

• setter访问时引发PropertyChanged事件
• 事件引发正确（属性名称等于引发事件的参数）

以下代码可以用作库，并显示如何测试以下泛型类

using System.ComponentModel;
using System.Linq;

/// <summary>
/// Check if every property respons to INotifyPropertyChanged with the correct property name
/// </summary>
public static class NotificationTester
    {
        public static object GetPropertyValue(object src, string propName)
        {
            return src.GetType().GetProperty(propName).GetValue(src, null);
        }

        public static bool Verify<T>(T inputClass) where T : INotifyPropertyChanged
        {
            var properties = inputClass.GetType().GetProperties().Where(x => x.CanWrite);
            var index = 0;

            var matchedName = 0;
            inputClass.PropertyChanged += (o, e) =>
            {
                if (properties.ElementAt(index).Name == e.PropertyName)
                {
                    matchedName++;
                }

                index++;
            };

            foreach (var item in properties)
            { 
                // use setter of property
                item.SetValue(inputClass, GetPropertyValue(inputClass, item.Name));
            }

            return matchedName == properties.Count();
        }
    }

阶级

---

我在这里做了一个扩展：

public static class NotifyPropertyChangedExtensions
{
    private static bool _isFired = false;
    private static string _propertyName;

    public static void NotifyPropertyChangedVerificationSettingUp(this INotifyPropertyChanged notifyPropertyChanged,
      string propertyName)
    {
        _isFired = false;
        _propertyName = propertyName;
        notifyPropertyChanged.PropertyChanged += OnPropertyChanged;
    }

    private static void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == _propertyName)
        {
            _isFired = true;
        }
    }

    public static bool IsNotifyPropertyChangedFired(this INotifyPropertyChanged notifyPropertyChanged)
    {
        _propertyName = null;
        notifyPropertyChanged.PropertyChanged -= OnPropertyChanged;
        return _isFired;
    }
}

用法如下：

   [Fact]
    public void FilesRenameViewModel_Rename_Apply_Execute_Verify_NotifyPropertyChanged_If_Succeeded_Through_Extension_Test()
    {
        //  Arrange
        _filesViewModel.FolderPath = ConstFolderFakeName;
        _filesViewModel.OldNameToReplace = "Testing";
        //After the command's execution OnPropertyChanged for _filesViewModel.AllFilesFiltered should be raised
        _filesViewModel.NotifyPropertyChangedVerificationSettingUp(nameof(_filesViewModel.AllFilesFiltered));
        //Act
        _filesViewModel.ApplyRenamingCommand.Execute(null);
        // Assert
        Assert.True(_filesViewModel.IsNotifyPropertyChangedFired());

    }

---

较短版本：myClass.PropertyChanged+=（对象发送者，e）=>receivedEvents.Add（e.PropertyName）；第二个链接已关闭。我尝试了这个方法，但是如果我的属性设置器都有一个像“if（value==\u myValue）return”这样的保护语句（我所有的属性设置器都有），那么上面的方法就不会起作用，除非我遗漏了什么。我最近从C++到C语言。漂亮-你应该考虑打包它，并把它发布到NuGig.OrgWork工作！我非常喜欢fluent的API。我自己也做过类似的事情（），但我认为你的方法更简洁。

using System.ComponentModel;

public class TestMyClassWithINotifyPropertyChangedInterface : INotifyPropertyChanged
{
        public event PropertyChangedEventHandler PropertyChanged;

        protected void NotifyPropertyChanged(string name)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }
        }

        private int id;

        public int Id
        {
            get { return id; }
            set { id = value;
                NotifyPropertyChanged("Id");
            }
        }
}

public static class NotifyPropertyChangedExtensions
{
    private static bool _isFired = false;
    private static string _propertyName;

    public static void NotifyPropertyChangedVerificationSettingUp(this INotifyPropertyChanged notifyPropertyChanged,
      string propertyName)
    {
        _isFired = false;
        _propertyName = propertyName;
        notifyPropertyChanged.PropertyChanged += OnPropertyChanged;
    }

    private static void OnPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        if (e.PropertyName == _propertyName)
        {
            _isFired = true;
        }
    }

    public static bool IsNotifyPropertyChangedFired(this INotifyPropertyChanged notifyPropertyChanged)
    {
        _propertyName = null;
        notifyPropertyChanged.PropertyChanged -= OnPropertyChanged;
        return _isFired;
    }
}

   [Fact]
    public void FilesRenameViewModel_Rename_Apply_Execute_Verify_NotifyPropertyChanged_If_Succeeded_Through_Extension_Test()
    {
        //  Arrange
        _filesViewModel.FolderPath = ConstFolderFakeName;
        _filesViewModel.OldNameToReplace = "Testing";
        //After the command's execution OnPropertyChanged for _filesViewModel.AllFilesFiltered should be raised
        _filesViewModel.NotifyPropertyChangedVerificationSettingUp(nameof(_filesViewModel.AllFilesFiltered));
        //Act
        _filesViewModel.ApplyRenamingCommand.Execute(null);
        // Assert
        Assert.True(_filesViewModel.IsNotifyPropertyChangedFired());

    }