When creating test users display email/password returned, or store both and always display

Yeah... there's currently not way of getting at the user passwords for test users unless you do something like this:

function fb_test_create_form_submit($form, &$form_state) {

/* ... stuff ... */

      $result = $fb->api($fb_app->id . "/accounts/test-users", 'POST', array(
                           'installed' => $values['installed'],
                           'permissions' => $values['perms'],
                           'access_token' => fb_get_token($fb),
                         ));
      // Display the test user returned from fb
      dpm($result);

/* ... more stuff ... */
}

This makes it impossible (without the dpm) to create some test users, then click "login", fill out the form and see what happens. You can only login with the access token link then test your site as an already-logged-in user.