/**
  * Unregistering while not registers won't fail.
  *
  * @test
  */
 public function unregisterWhenNotRegistered()
 {
     // Unregister possible registered URL wrapper.
     vfsStreamWrapper::unregister();
     $this->assertNotContains(vfsStream::SCHEME, stream_get_wrappers());
     vfsStreamWrapper::unregister();
 }