private function _createFixture()
{
$customer = new ECommerceCustomer();
$customer->setName('Luke Skywalker');
$mentor = new ECommerceCustomer();
$mentor->setName('Obi-wan Kenobi');
$customer->setMentor($mentor);
$this->_em->persist($customer);
$this->_em->flush();
$this->_em->clear();
}