Estoy tratando de probar el correo electrónico en la prueba funcional ...

Mi código fuente es el mismo que elejemplo del libro de cocina,

el controlador :

public function sendEmailAction($name)
{
    $message = \Swift_Message::newInstance()
        ->setSubject('Hello Email')
        ->setFrom('[email protected]')
        ->setTo('[email protected]')
        ->setBody('You should see me from the profiler!')
    ;

    $this->get('mailer')->send($message);

    return $this->render(...);
}

Y la prueba:

// src/Acme/DemoBundle/Tests/Controller/MailControllerTest.php
use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;

class MailControllerTest extends WebTestCase
{
    public function testMailIsSentAndContentIsOk()
    {
        $client = static::createClient();

        // Enable the profiler for the next request (it does nothing if the profiler is not available)
        $client->enableProfiler();

        $crawler = $client->request('POST', '/path/to/above/action');

        $mailCollector = $client->getProfile()->getCollector('swiftmailer');

        // Check that an e-mail was sent
        $this->assertEquals(1, $mailCollector->getMessageCount());

        $collectedMessages = $mailCollector->getMessages();
        $message = $collectedMessages[0];

        // Asserting e-mail data
        $this->assertInstanceOf('Swift_Message', $message);
        $this->assertEquals('Hello Email', $message->getSubject());
        $this->assertEquals('[email protected]', key($message->getFrom()));
        $this->assertEquals('[email protected]', key($message->getTo()));
        $this->assertEquals(
            'You should see me from the profiler!',
            $message->getBody()
        );
    }
}

sin embargo me salió este error:

Error fatal de PHP: llamar a una función miembro getCollector () en un no objeto

El problema viene de esta línea:

$mailCollector = $client->getProfile()->getCollector('swiftmailer');

alguna idea ?