Test for caching header
It would be very useful to have a way to test for caching status. In my case, when caching reverts to bypass mode, my site performance takes a hit! I currently have no way to know if we hit bypass until a user reports an 503 error. Most of the sites I manage are news organizations, so our traffic often goes from a baseline of around 10s of requests per minute to thousands of requests per minute. The cache bypasses are often caused by a wordpress plugin that decides to start a session or add a server side cookie to EVERY pageview!
I could imagine this could be as simple as adding an additional set of options in the "contains" setting of a check that looks at the response http headers for a specific key/value. In my case it would simply be x-gateway-cache-status is not equal to "BYPASS" ... or conversely equals either "HIT" or "MISS"