I recently added the ability to spin up Katello clients via
subscription-manager and katello-agent to katello-deploy using docker.
These containers provide the ability to spin up any of our supported OS
clients with a working katello-agent that will register to a
Foreman/Katello and is ready for testing package installation/update/etc.
You can also do scale testing by using docker-composes scale functionality.
See  for more details and setup.