This is kind of a wishlist item; I may implement it myself. It'd be nice if test accounts could be flagged as such in the database. In other words, in cases where account creation is tested regularly after the site is on production, the test accounts would have a field set on the fe_user record that could be used to purge them.
My initial thinking is that a technical user could easily set a cookie in their browser, and cicregister would see this and, probably through a decorator, set a value on the fe_user.