Elgg\Http\ResponseFactoryTest::testCanNotSendModifiedResponse PHP Method

    public function testCanNotSendModifiedResponse()
    {
        $service = $this->createService();
        $response = $service->prepareResponse('foo');
        ob_start();
        $sent_response = $service->send($response);
        ob_get_clean();
        $this->assertInstanceOf(Response::class, $sent_response);
        $response->headers->set('X-Elgg-Modified', '1');
        $this->assertEquals($sent_response, $service->send($response));
    }