我有一些引发PropertyChanged
事件的代码,我希望能够对事件正确引发的单元测试进行测试。
提升事件的代码就像
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");
}
}
}
}
我从单元测试中的以下代码中获得了一个很好的绿色测试,它使用了委托:
[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);
}
然而,如果我然后尝试将属性的设置链接在一起,如下:
public string MyProperty
{
set
{
if (_myProperty != value)
{
_myProperty = value;
NotifyPropertyChanged("MyProperty");
MyOtherProperty = "SomeValue";
}
}
}
public string MyOtherProperty
{
set
{
if (_myOtherProperty != value)
{
_myOtherProperty = value;
NotifyPropertyChanged("MyOtherProperty");
}
}
}
我对该事件的测试失败 - 它捕获的事件是MyOtherProperty的事件。
我非常确定事件会触发,我的UI会像它一样做出反应,但我的代表只捕获最后一个要触发的事件。
所以我想知道:
1.我测试事件的方法是否正确?
2.我提高链式事件的方法是否正确?
答案 0 :(得分:166)
你所做的一切都是正确的,只要你想让你的测试问“最后一个被引发的事件是什么?”
您的代码按此顺序触发了这两个事件
这是否“正确”取决于这些事件的目的。
如果您想测试引发的事件数量以及引发它们的顺序,您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]);
}
答案 1 :(得分:19)
如果您正在进行TDD,那么事件测试可以开始生成重复代码的批次。我编写了一个事件监视器,可以为这些情况提供更清晰的单元测试编写方法。
var publisher = new PropertyChangedEventPublisher();
Action test = () =>
{
publisher.X = 1;
publisher.Y = 2;
};
var expectedSequence = new[] { "X", "Y" };
EventMonitor.Assert(test, publisher, expectedSequence);
有关详细信息,请参阅我对以下内容的回答。
Unit testing that an event is raised in C#, using reflection
答案 2 :(得分:8)
这是非常古老的,可能甚至不会被阅读,但有一些很酷的新.net功能我创建了一个INPC Tracer类,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);
}
答案 3 :(得分:5)
下面是一个略微改变的安德鲁代码,而不仅仅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"]);
}
答案 4 :(得分:1)
基于这篇文章,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);
}
使用此方法帮助程序,测试变得非常简单。
[TestMethod()]
public void Event_UserName_PropertyChangedWillBeFired()
{
var user = new User();
AssertPropertyChanged(user, (x) => x.UserName = "Bob", "UserName");
}
答案 5 :(得分:1)
不要为每个成员编写测试 - 这是很多工作
(也许这个解决方案并不适用于所有情况 - 但它显示了一种可能的方式。您可能需要根据您的使用情况进行调整)
可以在库中使用反射来测试您的成员是否都正确响应了您的属性更改事件:
以下代码可用作库,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();
}
}
现在可以将您班级的考试写成。 (也许你想把测试分成“事件在那里”和“用正确的名字提出的事件” - 你可以自己做)
[TestMethod]
public void EveryWriteablePropertyImplementsINotifyPropertyChangedCorrect()
{
var viewModel = new TestMyClassWithINotifyPropertyChangedInterface();
Assert.AreEqual(true, NotificationTester.Verify(viewModel));
}
类
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");
}
}
}
答案 6 :(得分:0)
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;
}
}
有用法:
[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());
}