postFoo example

public function testInitialState()
    {
        $this->assertEquals([], $this->dispatcher->getListeners());
        $this->assertFalse($this->dispatcher->hasListeners(self::preFoo));
        $this->assertFalse($this->dispatcher->hasListeners(self::postFoo));
    }

    public function testAddListener()
    {
        $this->dispatcher->addListener('pre.foo', [$this->listener, 'preFoo']);
        $this->dispatcher->addListener('post.foo', $this->listener->postFoo(...));
        $this->assertTrue($this->dispatcher->hasListeners());
        $this->assertTrue($this->dispatcher->hasListeners(self::preFoo));
        $this->assertTrue($this->dispatcher->hasListeners(self::postFoo));
        $this->assertCount(1, $this->dispatcher->getListeners(self::preFoo));
        $this->assertCount(1, $this->dispatcher->getListeners(self::postFoo));
        $this->assertCount(2, $this->dispatcher->getListeners());
    }

    public function testGetListenersSortsByPriority()
    {
        $listener1 = new TestEventListener();