Raising events

Let's say - for argument's sake - that we have an interface that has an event defined:

public interface IRobot
    event EventHandler FellInLove;

Now in a test where we have a faked instance of this interface we can raise that event whenever we want, specifying sender and event args. We could also omit the sender and the Fake will be passed as sender to the event handler. There's also a convenience method for raising with empty event args.

var robot = A.Fake<IRobot>();

robot.FellInLove += (s, e) =>

// Raise the event!
robot.FellInLove += Raise.With(someEventArgs); // the "sender" will be robot

// Use the overload for empty event args
robot.FellInLove += Raise.WithEmpty(); // sender will be robot, args will be EventArgs.Empty

// Specify sender and event args explicitly:
robot.FellInLove += Raise.With(sender: robot, e: someEventArgs);

Events of type EventHandler<TEventArgs> can be raised in exactly the same way.

Note that as of version 3.1.0, for the .NET Standard version of the FakeItEasy library, TEventArgs need not extend EventArgs to support the above syntax. The .NET 4.0 library still requires TEventArgs to extend EventArgs.

If an event is defined using a custom delegate, then Raise needs a typeparam to help it out:

public delegate void CustomEventHandler(object sender, CustomEventArgs e);
public delegate void FreeformEventHandler(int count);
event CustomEventHandler CustomEvent;
event FreeformEventHandler FreeformEvent;
fake.CustomEvent += Raise.With<CustomEventHandler>(fake, sampleCustomEventArgs);
fake.FreeformEvent += Raise.With<FreeformHandler>(7);

Just as when we're trying to override a method's behavior, for FakeItEasy to raise an event, the event must be virtual (if defined on a class) or defined on an interface.


AddHandler robot.FellInLove, Raise.With(EventArgs.Empty)