public function testSetGetDownloader()
 {
     $downloader = $this->createDownloaderMock();
     $manager = new DownloadManager(false, $this->filesystem);
     $manager->setDownloader('test', $downloader);
     $this->assertSame($downloader, $manager->getDownloader('test'));
     $this->setExpectedException('InvalidArgumentException');
     $manager->getDownloader('unregistered');
 }