public function testAddSurrogateEsiCapability() {
$esi = new Esi();
$request = Request::create('/');
$esi
->addSurrogateEsiCapability($request);
$this
->assertEquals('symfony2="ESI/1.0"', $request->headers
->get('Surrogate-Capability'));
$esi
->addSurrogateEsiCapability($request);
$this
->assertEquals('symfony2="ESI/1.0", symfony2="ESI/1.0"', $request->headers
->get('Surrogate-Capability'));
}