So I spent a while looking into making the job enumerator injectable (e.g. composition as you suggested), and teasing that apart isn't going to be a simple refactoring I can do in a few minutes.  It depends on several things currently managed by the worker (the logger, the reserver and the new `log` method that adds the pid to the logged message).  Given that the reserver is already injectable, it starts to get weird to have the job enumerator be injectable weird, or making the injection being the job enumerator class name and making the worker responsible for instantiating it and passing expected args.

Given the state of our prod environment, I've got other things that seem more important to work on right now.  Do you mind if I open an issue for this and we merge with this as-is for now?