测试环境中的Symfony PDO连接

i have a symfony environment running on a docker setup. Via docker-compose.yml (version 2) I start several containers. Following containers a relevant here:

phpfpm, nginx and mariadb

If i open my symfony project via browser it successfully connects to my database (on container called "mariadb"). Records from tables in my database are displayed. Even if i execute console commands to update my database schema it will work and changes are applied to my database.

Now i want to write functional / integration tests that run test against a second database on the same host (mariadb).

This is how i try to connect:

$dsn = sprintf(
        'mysql:host=%s;port=%s',
        'mariadb',
        3306
    );

$pdo = new PDOConnection(
    $dsn,
    'otk_dbuser',
    'testpass'
);

But the result is the following message:

SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: Name or service not known
  /opt/project/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOConnection.php:47
  /opt/project/src/TestingBundle/Tests/DatabaseTestCase.php:56
  /opt/project/src/TestingBundle/Tests/DatabaseTestCase.php:18

Could you please give me some help?

Kind regards, Max

Forget what i just asked. I executed my functional test within PHPStorm. PHPStorm uses therefore a standalone docker container, that has nothing todo with my docker-compose setup.

Dumb me!