Test of a method doing a generation of URL

Paginator.php

<?php

namespace Canopy\CoreBundle\Service;

use Doctrine\ORM\EntityManager;
use Symfony\Bundle\FrameworkBundle\Routing\Router;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
//…

class Paginator
{
    //…
    /**
     * Gets the the previous page's url according to the current page
     * and the filters provided, or null if there is no previous page.
     *
     * @param integer      $page       Current page
     * @param string       $repository Namespace of the the repository of the resource.
     * @param array | null $filters    Array of filters given to restrict the results.
     *
     * @return string | null
     */
    public function getPreviousUrl($page, $repository, array $filters = null)
    {
        if (1 == $page || 1 === $this->getTotalPages($repository, $filters)) {
            return null;
        }

        $parameters = array('page' => $this->getPreviousPage($page));

        if ($filters) {
            $parameters = array_merge($parameters, array('category' => $filters['category']));
        }

        return $this->router->generate(
            'canopy_get_notifications',
            $parameters,
            UrlGeneratorInterface::ABSOLUTE_URL
        );
    }
}   

PaginatorTest.php

<?php

namespace Canopy\CoreBundle\Tests\Service;

use Canopy\CoreBundle\Service\Paginator;
use Canopy\CoreBundle\Tests\Fake\FakeRepository;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;

class PaginatorTest extends \PHPUnit_Framework_TestCase
{
    private $em;
    private $router;
    private $fakeRepository;
    private $paginator;

    public function testGetPreviousPageT
    {
        $this->fakeRepository->expects($this->any())
            ->method('getTotalCount')
            ->will($this->returnValue(30)
        );
    
        // I make sure that the method is called one time with the right parameters, instead of
        // testing that the router workds well by generating the URL.
        $this->router->expects($this->once())
            ->method('generate')
            ->with('canopy_get_notifications', array('page' => 1), UrlGeneratorInterface::ABSOLUTE_URL)
        ;

        $this->paginator->getPreviousUrl(2, $this->fakeRepository);
    }

    public function setUp()
    {
        $this->em = $this->getMockBuilder('\Doctrine\ORM\EntityManager')
            ->disableOriginalConstructor()
            ->getMock(array('getRepository'))
        ;

        $this->router = $this->getMockBuilder('Symfony\Bundle\FrameworkBundle\Routing\Router')
            ->disableOriginalConstructor()
            ->getMock(array('generate'))
        ;

        $this->fakeRepository = $this->getMockBuilder('Canopy\CoreBundle\Tests\Fake\FakeRepository')
            ->disableOriginalConstructor()
            ->getMock(array('getTotalCount'))
        ;

        $this->em->expects($this->any())
            ->method('getRepository')
            ->will($this->returnValue($this->fakeRepository)
        );

        $this->paginator = new Paginator($this->em, $this->router, 10);
    }

    public function tearDown()
    {
        $this->em             = null;
        $this->router         = null;
        $this->fakeRepository = null;
        $this->paginator      = null;
    }