public function testTypeConversion()
{
$builder = $this->dm->createAggregationBuilder('Documents\\User');
$date = new \DateTime();
$mongoDate = new \MongoDate($date->format('U'), $date->format('u'));
$stage = $builder->match()->field('createdAt')->lte($date);
$this->assertEquals(['$match' => ['createdAt' => ['$lte' => $mongoDate]]], $stage->getExpression());
}