public function testPreserveId() {
		$model = $this->_model;
		$model::config(array('connection' => 'lithium_mongo_test', 'source' => 'posts'));

		$document = $model::create(array('_id' => 'custom'));
		$document->save();

		$document->_id = 'custom2';
		$document->foo = 'bar';
		$this->assertTrue($document->save());
		$this->assertNull($model::first('custom2'));
		$this->assertEqual(array('_id' => 'custom'), $model::first('custom')->data());
	}