为事件处理程序编写单元测试C＃

Question

I need a test case for testing event handlers. In my project, I just pass the total file size value from the Model class to ViewModel class using event handlers.

What are all the ways to write test case for event handlers and what I have to do in my test case?

My test case is not working..

View Model

public RipWatcherWindowShellViewModel(IWorkflowManager workflowManager)
{
    WorkflowManager = workflowManager;
    workflowManager.GetTotalUsfFileSize += workflowManager_GetTotalFileSize;
}


/// <summary>Delegate for workflowManager get total file size</summary>
/// <param name="sender">The sender object</param>
/// <param name="e">The FileSizeChangedEventArgs object</param>
public void workflowManager_GetTotalFileSize(object sender, FileSizeChangedEventArgs e)
{
    if(e.FileSize== 0)
    {
        throw new ArgumentException("We cannot calculate progress percentage because total file size is 0");
    }
    TotalUsfFileSize = e.FileSize;
}

Model

public class WorkflowManager
{

    public event EventHandler<FileSizeChangedEventArgs> GetTotalUsfFileSize;

    public void StartWorkflow()
    {           
        totalFileSize= jobWatcher.StartWatching(HotFoldersCollection);

         //Event handler Raised here....

        GetTotalUsfFileSize.SafeInvoke(this, new FileSizeChangedEventArgs(totalFileSize));
     }
  }

Event Handler

public class FileSizeChangedEventArgs:EventArgs
{

    public FileSizeChangedEventArgs (Double fileSize)
    {
        FileSize = fileSize;
    }

    public Double FileSize
    {
        get;
        private set;
    }
}

My Test case

[Test]
public void IsGetTotalFileSizeEventFired()
{
    worflowManager = new Mock<IWorkflowManager>().Object;

    ripWatcherWindowShellViewModel = new RipWatcherWindowShellViewModel(worflowManager);
    ripWatcherWindowShellViewModel.GetTotalUsfFileSize += delegate { eventRaised = true; };

    Assert.IsTrue(eventRaised);
}

Answer 1

If you are testing that your event handler works, simply call the event handler with the event args that you want to test.

In your case I assume you want to test that your event is raised. This will be dependent on if any calls inside your StartWorkFlow have any external dependencies (like to the actual file system. If it does, then you are crossing over into integration test territory and no longer unit test territory). In that instance, make sure jobWatcher is also mocked, or make StartWorkFlow virtual so that you can alter its behavior to suit your test.