public function testSetId_AsMongoIdClass()
{
// save document
$id = new \MongoId();
$doc = $this->collection->createDocument(array('a' => 'a'));
$doc->setId($id);
$doc->save();
// find document
$this->assertNotEmpty($this->collection->getDocument($id));
// delete document
$this->collection->deleteDocument($doc);
}