public function testAddCustomGroupMediaItemsFieldsWithItemInterface()
{
$feed = $this->manager->get('article');
$feed->add(new FakeItemInterfaceEntity());
$feed->addItemField(new GroupItemField('images', new MediaItemField('getFeedMediaMultipleItems')));
$output = $feed->render('atom');
$this->assertContains('<images>', $output);
$this->assertContains('<link rel="enclosure" href="http://website.com/image.jpg" type="image/jpeg" length="500"/>', $output);
$this->assertContains('<link rel="enclosure" href="http://website.com/image2.png" type="image/png" length="600"/>', $output);
$this->assertContains('</images>', $output);
}