Symfony TestCase using fixtures and database transactions

FixtureTestCase.php

<?php

use Doctrine\Bundle\DoctrineBundle\Registry;
use Doctrine\Common\Persistence\ObjectManager;
use Doctrine\DBAL\Connection;
use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;

class FixtureTestCase extends KernelTestCase
{
    /**
     * @var Registry
     */
    protected $doctrine;

    /**
     * @var ObjectManager
     */
    protected $manager;

    /**
     * @var Connection
     */
    protected $db;

    public function setUp() : void
    {
        static $kernel;

        if (null === $kernel || null === $kernel->getContainer()) {
            $kernel = self::bootKernel();
        }

        $this->doctrine = $kernel->getContainer()->get('doctrine');
        $this->manager  = $this->doctrine->getManager();
        $this->db       = $kernel->getContainer()->get('database_connection');

        $this->db->beginTransaction();
    }

    /**
     * @throws \Doctrine\DBAL\ConnectionException
     */
    public function tearDown() : void
    {
        $this->db->rollBack();
    }

    protected function factory() : Factory
    {
        return Factory::create($this->manager);
    }
}