How can QA staff test caching logic that they can't see?

I just implemented a caching layer in my web application, and now I'm wondering how QA is supposed to test it, since caching is transparent to the user.

One idea I have is to put logging in the methods that invoke the code that populate the cache, and record when an object is pulled from cache and when it requires recreation from the database, and then the testers could view the logs to see if, for example, a certain object is reloaded from the db every 10 minutes, instead of every page view.

But can anyone suggest some better practices for this situation?