public static function drop_site($displayprogress = false) {
        global $DB, $CFG;

        if (!self::is_test_site()) {
            phpunit_bootstrap_error(PHPUNIT_EXITCODE_CONFIGERROR, 'Can not drop non-test site!!');
        }

        // Purge dataroot
        if ($displayprogress) {
            echo "Purging dataroot:\n";
        }

        self::reset_dataroot();
        testing_initdataroot($CFG->dataroot, 'phpunit');

        // Drop all tables.
        self::drop_database($displayprogress);

        // Drop dataroot.
        self::drop_dataroot();
    }