public function testAddSurrogateControl() {
$esi = new Esi();
$response = new Response('foo <esi:include src="" />');
$esi
->addSurrogateControl($response);
$this
->assertEquals('content="ESI/1.0"', $response->headers
->get('Surrogate-Control'));
$response = new Response('foo');
$esi
->addSurrogateControl($response);
$this
->assertEquals('', $response->headers
->get('Surrogate-Control'));
}