How to check if a View was cached?
Caching only works for anonymous users (people who are not logged in). 

So, a simple test would be to add new content to your view or make a change to your view. Ex: change your view title. 

On another browser have your page open, but as anonymous. If your view doesn't change, it means the cache worked. 

The View will NOT change to anonymous users until you clear the cache.