Great work! Thank you.
If there have some option related with user role or group, the plugin can be 100% complete. In my case, I would like to give some different tests to users who are s2member-level1 for instance. Furthermore, the test can be activated in pre-defined time period. These functions will save real timing for teachers who use this plugin.
FYI: I found one of nice plugin http://wordpress.org/support/view/plugin-reviews/user-groups that co-works with s2member. There doesn't have any crash with these two.
Thank you again