public function testMongoIdPreservation()
{
$post = MockMongoPost::create(array('_id' => new MongoId(), 'title' => 'A post'));
$post->save();
$result = array_pop($this->_db->connection->queries);
$data = $result['data'];
$this->assertEqual('A post', $data['title']);
$this->assertInstanceOf('MongoId', $data['_id']);
$post->sync();
$post->title = 'An updated post';
$post->save();
$result = array_pop($this->_db->connection->queries);
$this->assertEqual(array('_id' => $post->_id), $result['conditions']);
$this->assertEqual(array('$set' => array('title' => 'An updated post')), $result['update']);
}