var IRepository = new Mock<IRepository>();
Request request = new Request();
IRepository.Setup(a => a.Save(request)).Raises(a => a.Created += null, RequestCreatedEventArgs.Empty);

public class Request
    {
        //...
    }

    public class RequestCreatedEventArgs : EventArgs
    {
        Request Request {get; set;}
    }

    //=======================================
    //You must have sender as a first argument
    //=======================================
    public delegate void RequestCreatedEventHandler(object sender, RequestCreatedEventArgs e);

    public interface IRepository
    {
        void Save(Request request);
        event RequestCreatedEventHandler Created;
    }

    [TestMethod]
    public void Test()
    {
        var repository = new Mock<IRepository>();
        Request request = new Request();
        repository.Setup(a => a.Save(request)).Raises(a => a.Created += null, new RequestCreatedEventArgs());

        bool eventRaised = false;
        repository.Object.Created += (sender, e) =>
        {
            eventRaised = true;
        };
        repository.Object.Save(request);

        Assert.IsTrue(eventRaised);
    }

class IRepository
{
    public event THING Created;
}
class THING : EventArgs
{
    public static THING Empty
    {
        get { return new THING(); }
    }
}