Just a very basic snippet of purging entities and loading fixtures with Nelmio\Alice within a BehatContext

DataContext.php

<?php

namespace Context;

use Behat\Behat\Context\BehatContext,
    Behat\Symfony2Extension\Context\KernelAwareInterface;

use Nelmio\Alice as Fixtures;

// ...

/**
 * Data writing and reading context
 */
class DataContext extends BehatContext implements KernelAwareInterface
{
    // ...
    
    /**
     * E.g. ‘Given there are pages in the database’ loads pages.yml, and
     * ‘Given there are users and tasks in the database’ loads users_and_tasks.yml.
     *
     * Tables are purged as new entities are loaded in.
     *
     * @Given /^there (?:is|are) (.+) in the database$/
     */
    public function loadFixtures($fixtures)
    {
        $fixtures = preg_replace(array('/[^\w\s]/', '/\s+/'),
                                 array('',          '_'),
                                 $fixtures);

        $loader  = new Fixtures\Loader\Yaml;
        $objects = $loader->load($this->getFixturesDir().$fixtures.'.yml');

        $em     = $this->getEntityManager();
        $purged = array();

        foreach ($objects as $object)
        {
            $class = get_class($object);

            if (in_array($class, $purged))
            {
                continue 1;
            }

            // Delete $class
            $q = $em->createQuery(sprintf('DELETE FROM %s', $class));
            $q->execute();

            $purged[] = $class;
        }

        $persister = new Fixtures\ORM\Doctrine($em);
        $persister->persist($objects);
    }

    // ...
}