Connection.php

<?php

namespace Drupal\driver_test\Driver\Database\DrivertestMysqlDeprecatedVersion;

include_once dirname(__DIR__, 8) . '/mysql/src/Driver/Database/mysql/Connection.php';
use Drupal\mysql\Driver\Database\mysql\Connection as CoreConnection;

/**
 * MySQL test implementation of \Drupal\Core\Database\Connection.
 */
class Connection extends CoreConnection {
  
  /**
   * Hardcoded database server version.
   *
   * Faking that we are on a deprecated database.
   *
   * @var string
   */
  protected $databaseVersion = '10.2.31-MariaDB-1:10.2.31+maria~bionic-log';
  
  /**
   * {@inheritdoc}
   */
  public function driver() {
    return 'DrivertestMysqlDeprecatedVersion';
  }
  
  /**
   * {@inheritdoc}
   */
  public function isMariaDb() : bool {
    return TRUE;
  }
  
  /**
   * {@inheritdoc}
   */
  public function version() {
    return $this->databaseVersion;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function getServerVersion() : string {
    return $this->databaseVersion;
  }

}