handle($request1); $this->assertEquals(200, $response1->getStatusCode()); $etag = $response1->getHeaderLine('ETag'); $this->assertNotEmpty($etag); $request2 = (new ServerRequest('GET', '/_phred/health')) ->withHeader('If-None-Match', $etag); $response2 = $kernel->handle($request2); $this->assertEquals(304, $response2->getStatusCode()); } }