Though I'm not sure your delegation will work here. What is the background why you need to delegate it in the first place? The normal way would be to apply the play to the hosts of the group test. I guess you're instead running the play against localhost?
Another unrelated thing: I experienced issues with the docker module when pull: always used together with state: reloaded. Unlike docker-compose, the docker module will always restart the container no matter if there was an updated image pulled or not.