Sokil\Mongo\DocumentRelationTest::testAddRelation_HasMany PHP Method

    public function testAddRelation_HasMany()
    {
        // collections
        $carsCollection = $this->database->getCollection('cars');
        $wheelsCollection = $this->database->getCollection('wheels');
        $wheelDocument = $wheelsCollection->createDocument(array('diameter' => 30))->save();
        $carDocument = $carsCollection->createDocument(array('brand' => 'Nissan'))->save()->addRelation('wheels', $wheelDocument);
        $this->assertEquals($carDocument->getId(), $wheelDocument->car_id);
    }