I'm looking for a module which will test an entire site with each OS update, or Drupal core update. E.g. go through each node and let me know there are any 404 returned for JS or CSS files, broken links, any white screens of death, etc. And if possible if the response time of the site has drastically decreased.

I've done some search and can I only see references to SimpleTest used or unit testing. I'm looking at using Selenium at the moment.

How are other people testing sites after a core changes?