The migration tests are currently not running

The error message:

Drupal\Tests\search404\Kernel\ValidateD6SettingsMigrationTest::testMigration
PHPUnit\Framework\Exception: PHP Fatal error: Uncaught AssertionError: The container was serialized. in /var/www/html/web/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php:82
Stack trace:
#0 /var/www/html/web/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php(82): assert(false, 'The container w...')
#1 [internal function]: Drupal\Core\DependencyInjection\ContainerBuilder->__sleep()
#2 Standard input code(84): serialize(Array)
#3 Standard input code(123): __phpunit_run_isolated_test()
#4 {main}
thrown in /var/www/html/web/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php on line 82
Fatal error: Uncaught AssertionError: The container was serialized. in /var/www/html/web/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php:82
Stack trace:
#0 /var/www/html/web/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php(82): assert(false, 'The container w...')
#1 [internal function]: Drupal\Core\DependencyInjection\ContainerBuilder->__sleep()
#2 Standard input code(84): serialize(Array)
#3 Standard input code(123): __phpunit_run_isolated_test()
#4 {main}
thrown in /var/www/html/web/core/lib/Drupal/Core/DependencyInjection/ContainerBuilder.php on line 82

/var/www/html/vendor/phpunit/phpunit/src/Framework/TestSuite.php:684
/var/www/html/vendor/phpunit/phpunit/src/TextUI/TestRunner.php:651
/var/www/html/vendor/phpunit/phpunit/src/TextUI/Command.php:144
/var/www/html/vendor/phpunit/phpunit/src/TextUI/Command.php:97

The problem seems to be coming from the "ValidateSettingsMigrationTrait", but I couldn't yet completely find out, what makes it fail.

Possibly similar or related issues:

• #3155313: Drupal 9 The container was serialized →
• 🌱 [META] Serialization issues in Migration tests Active

🌱 [META] Serialization issues in Migration tests Active is probably it. We should postpone this issue and disable the migration tests through 📌 Create tests to test this modules functionality Active .

POSTPONED on 🌱 [META] Serialization issues in Migration tests Active .