public function testWriteNull()
{
$response = new Response();
$this->service->writeNull($response);
$this->assertTrue($response->getHeaders()->has('SetCookie'));
$cookie = $response->getHeaders()->get('SetCookie')->current();
$this->assertInstanceOf('Zend\\Http\\Header\\SetCookie', $cookie);
$this->assertEquals('JwPersistentUser', $cookie->getName());
$this->assertDateTimeEquals(new \DateTime('-1 hour'), new \DateTime($cookie->getExpires()));
$this->assertEquals('/', $cookie->getPath());
}