Symfony\Component\HttpFoundation\Session::setFlash PHP Метод

    public function setFlash($name, $value)
    {
        if (false === $this->started) {
            $this->start();
        }

        $this->flashes[$name] = $value;
        unset($this->oldFlashes[$name]);
    }

 public function setUp()
 {
     $this->request = new Request();
     $session = new Session(new ArraySessionStorage());
     $session->set('foobar', 'bar');
     $session->setFlash('foo', 'bar');
     $this->request->setSession($session);
 }