Repository testing for DAO layer. Boot the kernel is required to get a valid database connection.

Symfony-4.1-RepositoryTestCase.php

<?php

namespace App\Tests\Repository;

use App\Entity\User;
use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;

class UserRepositoryTest extends KernelTestCase
{
    /**
     * @var \Doctrine\ORM\EntityManager
     */
    private $entityManager;

    protected function setUp()
    {
        $kernel = self::bootKernel();

        $this->entityManager = $kernel->getContainer()
            ->get('doctrine')
            ->getManager();
    }

    public function testUserFindAll()
    {
        $users = $this->entityManager
            ->getRepository(User::class)
            ->findAll()
        ;
        
        // compare asserts
        //$this->assertCount(10, $users);
        $this->assertTrue(true);
    }

    protected function tearDown()
    {
        parent::tearDown();

        $this->entityManager->close();
        $this->entityManager = null; // avoid memory leaks
    }
}