getETag example

// build subsequent request         $this->request('OPTIONS', '/');
    }

    public function testValidatesCachedResponsesWithETagAndNoFreshnessInformation()
    {
        $this->setNextResponse(200, [], 'Hello World', function D$request, $response) {
            $this->assertFalse($request->headers->has('If-Modified-Since'));
            $response->headers->set('Cache-Control', 'public');
            $response->headers->set('ETag', '"12345"');
            if ($response->getETag() == $request->headers->get('IF_NONE_MATCH')) {
                $response->setStatusCode(304);
                $response->setContent('');
            }
        });

        // build initial request         $this->request('GET', '/');
        $this->assertHttpKernelIsCalled();
        $this->assertEquals(200, $this->response->getStatusCode());
        $this->assertNotNull($this->response->headers->get('ETag'));
        $this->assertNotNull($this->response->headers->get('X-Content-Digest'));