Controller unit testing

Hello guys,

I'm having a hard time trying to test controllers and their actions. I don't understand, how should I properly test controller actions, since their execution usually doesn't return anything and everything is handled by the application. This is what I have so far:

Controller

class UserController extends Controller
{

    public function signInAction()
    {
        if ($this->auth->isAuthenticated()) {
            return $this->response->redirect();
        }

        $form = new UserSignInForm(new Users);
        $messages = array();

        if ($this->request->isPost()) {
            if ($form->isValid($_POST, $form->getEntity())) {
                try {
                    $this->auth->login($form->getValue('email'), $form->getValue('password'));
                    return $this->response->redirect();
                } catch (AuthenticationException $e) {
                    $messages[] = $e->getMessage();
                }
            } else {
                $messages = $form->getMessages();
            }
        }

        $this->view->form = $form;
        $this->view->messages = $messages;
    }

}

UnitTestCase

use Phalcon\DI;

abstract class UnitTestCase extends \PHPUnit_Framework_TestCase
{
    /**
     * @var Phalcon\DI
     */
    protected $di;

    /**
     * @var bool
     */
    private $_loaded = false;

    protected function setUp()
    {
        $this->checkExtension('phalcon');

        $this->di = DI::getDefault();
        $this->_loaded = true;
    }

    public function checkExtension($extension)
    {
        if (!extension_loaded($extension)) {
            $this->markTestSkipped("Warning: {$extension} extension is not loaded");
        }
    }

    /**
     * Check if the test case is setup properly
     * @throws \PHPUnit_Framework_IncompleteTestError;
     */
    public function __destruct() {
        if(!$this->_loaded) {
            throw new \PHPUnit_Framework_IncompleteTestError('Please run parent::setUp().');
        }
    }

}

UserControllerTest

class UserControllerTest extends \UnitTestCase
{

    public function testGetSignUpAction()
    {
        $controller = new UserController;
        $controller->signInAction();
    }

}

The signInActions returns no response nor any content, so I'm unable to make any assertions to check if the actions runs and renders the template properly.

What is the best practice here? Should my controllers manually render the desired templates or should I use $application->handle()->getContent(); with url to test the controller action reliably? Or just make requests via curl?

Thank you for your help!