Testing Lavavel Event Listener

I'm trying to test Event Listener in Laravel. This is my listener:

class FlashNotifier
{

    public function handleMenuItemWasStored()
    {
        Session::flash('flash-status', 'success');
        Session::flash('flash-message', 'Item was stored.');
    }

    public function subscribe($events)
    {
        $events->listen(
            MenuItemWasStored::class,
            '\App\Listeners\Menu\FlashNotifier@handleMenuItemWasStored'
        );
    }
}

And this is the test I came up so far:

public function testEventListenerWasTriggered()
{
    $listener = Mockery::mock('App\Listeners\Menu\FlashNotifier');
    $d = new Dispatcher;
    $listener->shouldReceive('handleMenuItemWasStored')->once();
    $d->fire('App\Events\Menu\MenuItemWasStored');
}

However, I get the following exception:

Mockery\Exception\InvalidCountException: Method     handleMenuItemWasStored() 
from Mockery_1_App_Listeners_Menu_FlashNotifier 
should be called  exactly 1 times but called 0 times.

What am I doing wrong?