public function testEmptyFilterCollection()
 {
     $filters = new FilterCollection();
     $this->assertFalse($filters->rewind());
     $this->assertFalse($filters->end());
     $this->assertFalse($filters->key());
     $this->assertFalse($filters->current());
     $this->assertFalse($filters->valid());
     $this->assertSame(0, count($filters));
 }