public function testCanNotValidateAlteredUrl()
{
$signed_url = $this->service->sign($this->url, '+1 hour');
$this->assertTrue($this->service->isValid($signed_url));
$signed_url = elgg_http_remove_url_query_element($signed_url, UrlSigner::KEY_EXPIRES);
$this->assertFalse($this->service->isValid($signed_url));
}