behat.yml

default:
    extensions:
      Behat\Symfony2Extension\Extension: ~
      Behat\MinkExtension\Extension:
        base_url: 'http://localadmin.example.com'
        selenium2: ~
        sahi: ~
        goutte: ~
        default_session: goutte
        javascript_session: sahi

FeatureContext.php

<?php

use Behat\Behat\Context\ClosuredContextInterface;
use Behat\Behat\Context\TranslatedContextInterface;
use Behat\Behat\Context\BehatContext;
use Behat\Behat\Context\Step;
use Behat\Behat\Exception\PendingException;

use Behat\Gherkin\Node\PyStringNode;

use Behat\Mink\Mink;
use Behat\MinkExtension\Context\MinkContext;
use Behat\MinkExtension\Context\MinkAwareInterface;

use Behat\Symfony2Extension\Context\KernelAwareInterface;

use Behat\CommonContexts\SymfonyDoctrineContext;

use Symfony\Component\HttpKernel\KernelInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

require_once 'PHPUnit/Autoload.php';
require_once 'PHPUnit/Framework/Assert/Functions.php';

/**
 * Features context.
 */
class FeatureContext extends BehatContext implements MinkAwareInterface, KernelAwareInterface
{
    private $mink;
    private $minkParameters;

    /**
     * @var KernelInterface $kernel
     */
    private $kernel;
    
    /**
     * Initializes context.
     */
    public function __construct()
    {
        $this->useContext('symfony_doctrine', new SymfonyDoctrineContext());
        $this->useContext('mink', new MinkContext());
    }

    /**
     * {@inheritdoc}
     */
    public function setMink(Mink $mink)
    {
        $this->mink = $mink;
    }

    /**
     * {@inheritdoc}
     */
    public function setMinkParameters(array $parameters)
    {
        $this->minkParameters = $parameters;
    }

    /**
     * {@inheritdoc}
     */
    public function setKernel(KernelInterface $kernel)
    {
        $this->kernel = $kernel;
    }

    /**
     * Returns the kernel's service container.
     *
     * @return ContainerInterface
     */
    public function getContainer()
    {
        return $this->kernel->getContainer();
    }
}

@everzet wow that's such a comprehensive reply! Thanks! Hopefully you can transform it into a doc article or cookbook entry.

1. I suppose it's common for a Symfony2 application to put it in a bundle, however, I am trying to avoid having too much code in a bundle (remember your tweet about difference between Components, Bundles and Bridges) so I might try and go with 2.

Just tried it out and 2. seems to be working, so thanks very much for your time!