public void Panel_OnKeyDown_Invoke_CallsKeyDown(KeyEventArgs eventArgs) { var control = new SubPanel(); int callCount = 0; KeyEventHandler handler = (sender, e) => { Assert.Same(control, sender); Assert.Same(eventArgs, e); callCount++; }; // Call with handler. control.KeyDown += handler; control.OnKeyDown(eventArgs); Assert.Equal(1, callCount); // Remove handler. control.KeyDown -= handler; control.OnKeyDown(eventArgs); Assert.Equal(1, callCount); }