public function testIsRegistered()
 {
     if (in_array(Stream::PROTOCOL, stream_get_wrappers())) {
         Stream::unregister();
     }
     $this->assertFalse(in_array(Stream::PROTOCOL, stream_get_wrappers()));
     $this->assertFalse(Stream::isRegistered());
     //
     Stream::register();
     $this->assertTrue(in_array(Stream::PROTOCOL, stream_get_wrappers()));
     $this->assertTrue(Stream::isRegistered());
 }