Using a function only in hydration returns only one result

array(1) {
  [-1]=>
  array(1) {
    ["namedep"]=>
    string(25) "Jonathan W.Administration"
  }
}

    public function testConcatFunction()
    {
        $this->generateFixture();
        $arg = $this->_em->createQuery('SELECT CONCAT(m.name, m.department) AS namedep FROM Doctrine\Tests\Models\Company\CompanyManager m')
                         ->getArrayResult();

        $this->assertEquals(4, count($arg)); // fails with 1
    }

    protected function generateFixture()
    {
        $manager1 = new CompanyManager();
        $manager1->setName('Roman B.');
        $manager1->setTitle('');
        $manager1->setDepartment('IT');
        $manager1->setSalary(100000);

        $manager2 = new CompanyManager();
        $manager2->setName('Benjamin E.');
        $manager2->setTitle('');
        $manager2->setDepartment('HR');
        $manager2->setSalary(200000);

        $manager3 = new CompanyManager();
        $manager3->setName('Guilherme B.');
        $manager3->setTitle('');
        $manager3->setDepartment('Complaint Department');
        $manager3->setSalary(400000);

        $manager4 = new CompanyManager();
        $manager4->setName('Jonathan W.');
        $manager4->setTitle('');
        $manager4->setDepartment('Administration');
        $manager4->setSalary(800000);

        $this->_em->persist($manager1);
        $this->_em->persist($manager2);
        $this->_em->persist($manager3);
        $this->_em->persist($manager4);
        $this->_em->flush();
        $this->_em->clear();
    }