(difficulty: "easy", requires a Moodle instance with tens of users to have something meaningful to sort) Visit the bulk actions page in the admin section. Check that the users are ordered according to what 'users_order_by_sql()' returns for the users ordering. Apply some filters (only 'contains', 'isequalto', 'startswith' and 'endswith' would make sense) to the text fields like 'fullname', 'firstname', etc., plus those text fields defined in the 'showuseridentity' admin setting. Ensure that the users ordering respects the filter and behaves according to what PhpDoc says for 'users_order_by_sql()' and it's search parameter.