PHPUnit: Testing form submissions with session variables stored in Symfony2

I had a small test done in PHP for a Controller I had written in Symfony2:

class DepositControllerTest extends WebTestCase {

    public function testDepositSucceeds() {

        $this->crawler = self::$client->request(
            'POST',
            '/deposit',
            array( "amount" => 23),
            array(),
            array()
        );

        $this->assertEquals(
            "Deposit Confirmation",
            $this->crawler->filter("title")->text());
    }
}

Up to here, everything was great. Problem started when I realized I wanted to disable possible re-submissions while refreshing the page. So I added a small mechanism to send nonce on every submission.

It works something like this:

class ReplayManager {

    public function getNonce() {
        $uid = $this->getRandomUID();
        $this->session->set("nonce", $uid);
        return $uid;
    }

    public function checkNonce($cnonce) {

        $nonce = $this->session->get("nonce");

        if ($cnonce !== $nonce)
            return false;

        $this->session->set("nonce", null);
        return true;
    }
}

So I had to mofidy the controller to get the nonce when displaying the form, and consume it when submitting.

But now this introduces a problem. I cant make a request to POST /deposit because I dont know what nonce to send. I thought to requesting first GET /deposit to render the form, and setting one, to use it in the POST, but I suspect Symfony2 sessions are not working in PHPUnit.

How could I solve this issue? I would not want to go to Selenium tests, since they are significant slower, not to mention that I would have to rewrite A LOT of tests.

UPDATE: I add a very simplified version of the controller code by request.

class DepositController extends Controller{

    public function formAction(Request $request){

        $this->replayManager = $this->getReplayManager();
        $context["nonce"] = $this->replayManager->getNonce();

        return $this->renderTemplate("form.twig", $context);
    }

    protected function depositAction(){

        $this->replayManager = $this->getReplayManager();
        $nonce               = $_POST["nonce"];

        if (!$this->replayManager->checkNonce($nonce))
            return $this->renderErrorTemplate("Nonce expired!");

        deposit($_POST["amount"]);

        return $this->renderTemplate('confirmation.twig');
    }

    protected function getSession() {
        $session = $this->get('session');
        $session->start();
        return $session;
    }

    protected function getReplayManager() {
        return new ReplayManager($this->getSession());
    }

}