I've been maintaining an automated test suite for a fairly complex web application via mech for a while. mech++.

I see a few things you might want to look at in your code:

1. This snippet: cmp_ok($mech->form_name('login'), '==', undef, "Logged in correctly. Page no longer shows logout option."); Should probably say "Logged in correctly. Page no longer shows login option."
2. I'm guessing there is a mechanism for users to log out insead of remembering rm=logout. Instead of hard coding that, why not verify the logout functionality exists as displayed by the user and when the click it, it logs out.
3. Instead of just checking for $mech->success, perhaps you should check for some content in the page. Just because your CGI returns 200 doesn't mean that all is "ok".