xUnit: how to Assert other event of types then EventHandler<EventArgs>

问题

I'm a beginner in unit testing and I've been searching the net for couple of hours now and I still can't find the answer to my simple question.

I have a class with the following event:

event Action<ITagData> OnTagHandled

Now I want to write a unit test to assert if the event has been raised but when I write something like:

Assert.Raises<EventArgs>(handler => m_rssiHander.OnTagHandled += handler,
    handler => m_rssiHander.OnTagHandled -= handler, () => { });

I get an error like:

Cannot implicitly convert type System.EventHandler to System.Action

Can someone tell me how I can assert an event of type Action<T>?

回答1:

It is because handler is type of EventHandler<EventArgs> so m_rssiHander.OnTagHandled += handler will not work

you will have to change: event Action<ITagData> OnTagHandled

TO event Action<EventArgs> OnTagHandled for it to work or any child class of EventArgs and inherit ITagData interface

e.g.

class TagDataEventArgs: EventArgs, ITagData {}

and use it as: event Action<TagDataEventArgs> OnTagHandled

AND assert:

Assert.Raises<TagDataEventArgs>(handler => m_rssiHander.OnTagHandled += handler,
        handler => m_rssiHander.OnTagHandled -= handler, () => { });

回答2:

Finally I decided to do it like this:

 bool wasEventRaised = false;
 m_rssiHandler.OnTagHandled += data => { wasEventRaised = true;};

 // Act
 m_rssiHandler.ProcessTag(m_tag);

 // Assert
 Assert.True(wasEventRaised);

来源：https://stackoverflow.com/questions/52956862/xunit-how-to-assert-other-event-of-types-then-eventhandlereventargs