To test if your site or a specific resource is being cached, use webpagetest.org. After you enter a URL and run a test, you can review the details page. If Cloudflare is caching, the response headers show the following:
If you have access to a terminal or command line window, you can also check a particular resource by using this command:
curl -svo /dev/null http://<your_URL>
A miss status means that Cloudflare is not caching that particular resource. Expired means that the resource is no longer in the Cloudflare cache.
To learn more, see Cloudflare CF-Cache-Status responses.