/**
* It should provide a duplicate version of itself.
*/
public function testDuplicate()
{
$this->document->loadXml($this->getXml());
$duplicate = $this->document->duplicate();
$this->assertNotsame($this->document, $duplicate);
$this->assertNotsame($this->document->firstChild, $duplicate->firstChild);
$this->assertNotsame($this->document->firstChild->firstChild, $duplicate->firstChild->firstChild);
}