View real exceptions in Behat output with Mink+SymfonyDriver in your Symfony2 feature suite

config_test.yml

...

parameters:
    test.client.class:  Your\MainBundle\ExceptionalClient

ExceptionalClient.php

<?php

namespace Your\MainBundle;

use Symfony\Bundle\FrameworkBundle\Client;
use Symfony\Component\HttpKernel\HttpKernelInterface;

class ExceptionalClient extends Client
{
    static private $catchExceptions = true;
    private $isRequestAlreadyPerformed = false;

    static public function catchExceptions($catch = true)
    {
        self::$catchExceptions = (bool) $catch;
    }

    protected function doRequest($request)
    {
        if ($this->isRequestAlreadyPerformed) {
            $this->kernel->shutdown();
        } else {
            $this->isRequestAlreadyPerformed = true;
        }

        return $this->kernel->handle(
            $request, HttpKernelInterface::MASTER_REQUEST, self::$catchExceptions
        );
    }
}

FeatureContext.php

<?php

...

/**
 * @Given do not catch exceptions
 */
public function doNotCatchExceptions()
{
    if (!$this->getSession()->getDriver() instanceof SymfonyDriver) {
        throw new \RuntimeException('This step could be used only with SymfonyDriver');
    }

    $this->getSession()->getDriver()->getClient()->catchExceptions(false);
}

/**
 * @BeforeScenario @exceptions
 */
public function dontCatchExceptions()
{
    if (!$this->getSession()->getDriver() instanceof SymfonyDriver) {
        throw new \RuntimeException('@exceptions tag could be used only with SymfonyDriver');
    }

    $this->getSession()->getDriver()->getClient()->catchExceptions(false);
}

/**
 * @AfterScenario
 */
public function catchExceptions()
{
    if ($this->getSession()->getDriver() instanceof SymfonyDriver) {
        $this->getSession()->getDriver()->getClient()->catchExceptions(true);
    }
}

...