Example configuration from modules/mysql/src/test/resources/logback-test.xml:

<root level="INFO">
    <appender-ref ref="STDOUT"/>
</root>

<logger name="org.testcontainers" level="DEBUG"/>

However DockerLoggerFactory provides names that either start with 🐳 or "docker" and they go under the root hierarchy.
So effectively any logging level lower (ex. "DEBUG") than one declared in root ("INFO" in this case) is swallowed.