public void RemoveAllListenersRemovesListeners() { var e = new EventEmitter(); numberToTest = 0; e.On("data", IncrementNumber); e.On("data", IncrementNumberBy2); e.RemoveAllListeners("data"); Assert.That(() => e.RemoveListener("data", IncrementNumberBy2), Throws.Exception .TypeOf <DoesNotExistException>() .With.Message.EqualTo("Func [Void IncrementNumberBy2(System.Object)] does not exist to be removed.")); }