Question

When extracting web service calls into an abstraction so they can easily be tested without being reliant on the web service being online how can I abstract event handlers called automatically by the service? The issue I’m running into is that since the API I’m using (EWS) has every class internaled so I can’t create them. This turns into an issue when unit testing because I can’t say for example, when the event gets fired that it should do x, y and z.

How can I extract these event handlers with my own so I can easily mock them?

Answer 1

You’ll need to wrap the class in your own class supporting an interface. For example if your service usage looks like this:

var service = new SomeService();
service.SomeEvent =+ (o, e) => DoSomething(e);
service.DoStuff();

You’ll create an interface:

public interface ISomeService
{
    event EventHandler SomeEvent;
    void DoStuff();
}

And your implementing class:

public class SomeServiceWrapper : ISomeService
{
    private readonly SomeService _containedService;

    public event EventHandler SomeEvent;

    public SomeServiceWrapper()
    {
        _containedService = new SomeService();
        _containedService.SomeEvent += (o, e) => RaiseSomeEvent(e);
    }

    public void DoStuff()
    {
        _containedService.DoStuff();
    }

    private void RaiseSomeEvent(EventArgs e)
    {
        EventHandler evt = SomeEvent;
        if (evt != null)
        {
            evt(this, e);
        }
    }
}

Then you can create a dummy ISomeService via mocking or your own dummy class, and you use the ISomeService instance SomeServiceWrapper in production.

Hope that helps.