public function testExtract()
 {
     $crawler = new Crawler();
     $str = html_entity_decode(file_get_contents(__DIR__ . '/../../Resources/embedded_videos.html'));
     $crawler->addContent($str);
     $tubelink = TubeLink::create();
     $extractor = new IframeExtractor($tubelink);
     $generated = $extractor->extract($crawler);
     $this->assertCount(3, $generated);
 }