NOTE: This test require admin access and an external DB authentication plugin. Check you has configured the "Update users" option (auth_db | updateusers) to "Yes" in the User account synchronisation section. Also, you should mapping all the custom profile fields with the fields of the external database.
1. Setup some custom profile fields (at least one of each type: text, textarea, date...)
2. Setup moodle to use authentication with external DB.
3. Setup auth module to take all custom profile fields from external DB source.
4. Login with user, having such fields filled in external DB.
5. Check for custom profile fields were updated.
6. Setup auth module to update all custom fields in external source.
7. Update all custom fields and check if they are updated in external source.
8. Setup auth module to block editing of this fields.
9. Check user cannot edit them.