如何使用 XUnit 引发 NotifyCollectionChangedEventArgs

Question

我有一个 class 实现 INotifyCollectionChanged，我想测试是否针对特定场景引发了 CollectionChanged 事件。

我试过下面的代码，但出现编译器错误，到目前为止我找不到解决方案。

[Fact]  
public void RaiseOnAddition()
{
  Action addition = () => Collection["new key"] = 3;

  Assert.Raises<NotifyCollectionChangedEventArgs>(
    handler => Collection.CollectionChanged += handler, // compiler error
    handler => Collection.CollectionChanged -= handler, // compiler error
    addition);
}

Cannot implicitly convert type 'System.EventHandler<System.Collections.Specialized.NotifyCollectionChangedEventArgs>' to 'System.Collections.Specialized.NotifyCollectionChangedEventHandler'

问题在于 handler 是 EventHandler<NotifyCollectionChangedEventArgs> 我想要 NotifyCollectionChangedEventHandler<NotifyCollectionChangedEventArgs>.

注意：PropertyChanged (Assert.PropertyChanged) 有一个特定的函数要测试，但 CollectionChanged.

没有

Answer 1

我想除了做这样的事情别无选择，

[Fact]  
public void RaiseOnAddition()
{
  var timesRaised = 0;

  NotifyCollectionChangedEventHandler handler += () => ++timesRaised;

  Collection["new key"] = 3;

  Assert.Equals(1, timesRaised);

  NotifyCollectionChangedEventHandler handler -= () => ++timesRaised;
}

Answer 2

public class TestClass : INotifyCollectionChanged
{
  public event NotifyCollectionChangedEventHandler? CollectionChanged;

  public void RaiseCollectionChanged()
  {
    CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
  }
}

public class TestClassTests
{
  [Fact]
  public void RaiseOnAddition()
  {
    var counter = 0;
    var testee = new TestClass();
    testee.CollectionChanged += (s, e) => counter++;
    testee.RaiseCollectionChanged();
    testee.RaiseCollectionChanged();
    Assert.Equal(2, counter);
  }
}

如何使用 XUnit 引发 NotifyCollectionChangedEventArgs

How to raise NotifyCollectionChangedEventArgs with XUnit

c#

events

unit-testing

xunit

inotifycollectionchanged