Creating an admin user using datafixtures and fosuserbundle

This worked for me (i'm also using FOSUserBundle):

// Change the namespace!
namespace Acme\DemoBundle\DataFixtures\ORM;

use Doctrine\Common\DataFixtures\FixtureInterface;
use Doctrine\Common\Persistence\ObjectManager;
use Symfony\Component\DependencyInjection\ContainerAwareInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

class LoadUserData implements FixtureInterface, ContainerAwareInterface
{
    //.. $container declaration & setter

    public function load(ObjectManager $manager)
    {
        // Get our userManager, you must implement `ContainerAwareInterface`
        $userManager = $this->container->get('fos_user.user_manager');

        // Create our user and set details
        $user = $userManager->createUser();
        $user->setUsername('username');
        $user->setEmail('[email protected]');
        $user->setPlainPassword('password');
        //$user->setPassword('3NCRYPT3D-V3R51ON');
        $user->setEnabled(true);
        $user->setRoles(array('ROLE_ADMIN'));

        // Update the user
        $userManager->updateUser($user, true);
    }
}

Hope this helps someone! :)

Follow this section of the documentation.