public function testGetIterator()
 {
     $resolver = $this->getFilesystemResolver();
     $this->resolver->attach($resolver);
     $iterator = $this->resolver->getIterator();
     $this->assertInstanceOf('SplPriorityQueue', $iterator);
     $this->assertEquals(1, $iterator->count());
     $this->assertEquals($resolver, $iterator->top());
 }