gistfile1.php

<?php
/**
 * WebTestCase client-aware test case
 */
trait ClientAware
{
    /**
     * @var \Symfony\Bundle\FrameworkBundle\Client
     */
    private $client;

    /**
     * Sets up client
     */
    public function setUp()
    {
        $this->client = static::createClient();
    }

    /**
     * @return \Symfony\Component\DependencyInjection\ContainerInterface
     */
    public function getContainer()
    {
        return $this->client->getContainer();
    }
}

gistfile2.php

<?php
use \Doctrine\Common\DataFixtures;

/**
 * Purges DB, needs container
 */
trait PurgeDb
{

    use ClientAware {
        setUp as clientAwareSetUp;
    }

    /**
     * Calls ClientAware trait method
     */
    public function setUp()
    {
        $this->clientAwareSetUp();

        $em = $this->getContainer()->get('doctrine.orm.entity_manager');
        $purger = new DataFixtures\Purger\ORMPurger($em);
        $purger->purge();
    }
}

gistfile3.php

<?php
use \Symfony\Bundle\FrameworkBundle\Test\WebTestCase;

use PurgeDb;

class FakerTest extends WebTestCase
{

    use PurgeDb;

    public function testPurgeAndPopulateEntity()
    {
        /** @var $em \Doctrine\ORM\EntityManager */
        $em = $this->getContainer()->get('doctrine.orm.entity_manager');
        $this->assertEquals(
            0,
            count($em->getRepository('WtProMainBundle:User')->findAll())
        );

        $faker = new \My\Faker($this->getContainer());

        $populator = $faker->getPopulator();
        $populator->addEntity('Entity\User', 3);
        $populator->execute(
            $this->getContainer()->get('doctrine.orm.entity_manager')
        );

        $this->assertEquals(
            3,
            count($em->getRepository('WtProMainBundle:User')->findAll())
        );
    }
}