Question

I have this text loader class that I’m trying to write tests for. And one of it’s methods does a RaiseEvent with a CancelEventArgs parsed in as an argument, so something like this:

Private Sub FireThisEvent()
    cancelEvent created here
    RaiseEvent HelloWorld(cancelEvent)

    If cancelEvent.Cancel Then
        'do smthg
    End If
End Sub

The handler for HelloWorld event is my UI class that makes a pop-up for the user to
decide Yes or No, which then sets cancelEvent.Cancel to either True or False. And then the above method checks on cancelEvent and does an action accordingly.

My question is, since I’m only testing the loader class (and not the UI), how do I manipulate the cancelEvent after the event is raised so that I can test for when cancelEvent.Cancel is True and then , when it is False. Thank you.

Would I have mock the UI class?

Answer 1

My solution to this was to add an event handler in the test method, so that when the event is raised, the test method will create a CancelEventAgrs and set its Cancel to True/False.

Public Sub TestingMethod()
        Dim txt As TextLoader = Nothing
        AddHandler TextLoader.LoadingDoneEvent,
            (Sub(e As ComponentModel.CancelEventArgs)
                 e.Cancel = True
             End Sub)

        txt = New TextLoader()
        txt.FireThisEvent()
End Sub