How do you know that crawlers are actually visiting pages?

We are certain 100% that G crawlers are coming to pages because of our setup as well as non-stop in-house testing.

With all the links that we process of our own we have testing URLs where we post URLs in the mix just in order to get feedback about crawling status.

This is why we are certain that G spiders do visit each and every page we feed them.

Just please remember formula that it is simple as this:

NO GOOGLE-BOT CRAWLER VISIT = NO PAGE IN INDEX

It is really simple as that.