Can I test pages protected by either form based or basic authentication

Yes. You can take screenshots of pages 'behind the curtain' which require a user name and password to login before viewing the page. We have a blog post which explains the steps - http://crossbrowsertesting.com/blog/cross-browser-checks-pages-behind-user-name-password.

Note: Screenshots of pages protected by basic authentication does not work with the Opera and Konqueror browsers.