CI/CD, Phpunit: Not connecting to the database

I have the following problem while inserting phpunit inside ci/cd pipeline. The idea behind phpunit that I am using test database with fixtures, and I am deleting content inside tables between every single test, which absolutely works. Now since I am want to reproduce the same process inside ci/cd pipeline, I get this error message, that it is not possible to connect to the database.

$ php bin/console doctrine:database:drop --force --if-exists --env=test --connection=default
99In ExceptionConverter.php line 103:
100                                                                               
101  An exception occurred in the driver: SQLSTATE[HY000] [2002] php_network_get  
102  addresses: getaddrinfo for db failed: Name or service not known              
103                                                                               
104In Exception.php line 28:
105                                                                               
106  SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo for db failed:  
107   Name or service not known                                                   
108                                                                               
109In Driver.php line 28:
110                                                                               
111  SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo for db failed:  
112   Name or service not known                                                   
113                                                                               
114In Driver.php line 28:
115                                                                               
116  PDO::__construct(): php_network_getaddresses: getaddrinfo for db failed: Na  
117  me or service not known                  

My .env.test

# define your env variables for the test env here
KERNEL_CLASS='App\Kernel'
APP_SECRET='$ecretf0rt3st'
SYMFONY_DEPRECATIONS_HELPER=999999
PANTHER_APP_ENV=panther
PANTHER_ERROR_SCREENSHOT_DIR=./var/error-screenshots
# .env.test.local
DATABASE_URL="mysql://db:db@db:3306/testdb?serverVersion=mariadb-10.3.11&charset=utf8mb4"

CI/CD Pipeline (Gitlab)

phpunit:
  stage: test
  dependencies:
    - composer
  services:
    - name: mariadb:10.3.11
      alias: mysql
  variables:
    MYSQL_ROOT_PASSWORD: root
    MYSQL_DATABASE: testdb
    MYSQL_USER: root
    MYSQL_PASSWORD: root
    DATABASE_URL: mysql://root:root@db:3306/testdb?serverVersion=mariadb-10.3.11&charset=utf8mb4
  before_script:
    - php bin/console doctrine:database:drop --force --if-exists --env=test --connection=default
    - php bin/console cache:clear --env=test
    - php bin/console doctrine:database:create --env=test
    - php bin/console doctrine:migrations:migrate --env=test
    - php bin/console doctrine:fixtures:load
  script:
    - mkdir $TEST_DIR
    - vendor/bin/phpunit tests/ServiceTest --coverage-text --log-junit $TEST_DIR/junit.xml --coverage-clover $TEST_DIR/clover.xml
  cache:
    key: $CACHE_KEY
    paths:
      - ./vendor/

Snippet about testing that I did so far

class CartServiceTest extends WebTestCase
{
    public EntityManager $entityManager;
    public KernelBrowser $client;
    public Cart $cart;
    public User $user;

    public function setUp(): void
    {
        $this->client = static::createClient();
        $this->entityManager = $this->client->getContainer()
                                            ->get('doctrine')
                                            ->getManager();

        $userFixture = new UserFixtures();
        $user = $userFixture->load($this->entityManager);

        $productFixture = new ProductFixtures();
        $product = $productFixture->load($this->entityManager);

        $this->loginUser();
    }

    public function tearDown(): void
    {
        self::ensureKernelShutdown();
        $purger = new ORMPurger($this->entityManager);
        $purger->purge();
    }

    /**
     * Login User for Testing
     *
     * @return void
     */
    public function loginUser(): void
    {
        //Login User
        $userRepository = static::getContainer()->get(UserRepository::class);
        $this->user = $userRepository->findOneBy(['email' => 'testmail@gmail.com']);
        $this->client->loginUser($this->user);
    }


    //************************//
    //****** TESTING ******* //
    //**********************//


    /**
     * Test getCart()
     *
     * @return void
     */
    public function testgetCart(): void
    {
        //Create Cart (Method is going to be tested especially)
        $createCart = static::getContainer()->get(CartService::class)->getOrCreateCart();

        //Get Cart by User ID
        $cart = static::getContainer()->get(CartService::class)->getCart();

        //Customer
        $this->assertIsObject($this->user);
        $this->assertIsInt($this->user->getId());
        $this->assertEquals('testmail@gmail.com', $this->user->getEmail());
        $this->assertEquals('Test', $this->user->getFirstName());
        $this->assertEquals('User', $this->user->getLastName());
        $this->assertIsString($this->user->getFirstName());
        $this->assertIsString($this->user->getLastName());

        //Cart
        $this->assertIsInt($cart->getId());
        $this->assertIsObject($cart);
        $this->assertObjectHasAttribute('id', $cart);
        $this->assertObjectHasAttribute('customer', $cart);
        $this->assertObjectHasAttribute('totalprice', $cart);
    }

The project is running on ddev(docker) machine, with Symfony 5.4