public function testAddCustomGroupChannelFieldWithItemInterface()
{
$feed = $this->manager->get('article');
$feed->add(new FakeItemInterfaceEntity());
$feed->addChannelField(new GroupChannelField('image', [new ChannelField('name', 'My test image'), new ChannelField('url', 'http://www.example.com/image.jpg')]));
$output = $feed->render('rss');
$this->assertContains('<image>', $output);
$this->assertContains('<name>My test image</name>', $output);
$this->assertContains('<url>http://www.example.com/image.jpg</url>', $output);
$this->assertContains('</image>', $output);
}