In this post to his site Paul Jones introduces a tool that aims to help you and your Composer-centric workflow, making it easier to validate and release packages for your projects: Producer.
Back when I was working on Solar, we needed a process to package up each release of the entire framework and make sure I hadn’t forgotten anything. [...] After Solar was done, we began extracting its individual components as 30 or so separate packages in Aura.
[...] But now I have started some non-Aura projects: Relay, Radar, Arbiter, Bookdown, and most recently Atlas. These projects do not have the benefit of the automated release process, with all of its checks and validation, that Aura does.
With that in mind, then, I have extracted a substantial amount of the Aura package release process into a new project, Producer, so that I can use it with any non-Aura library package. That means you can use it with your library package, too.
He goes on to talk about why you might want to use Producer in your workflow and its functionality for validating and releasing packages. He also answers some of the common questions he's gotten about the tool, mostly around the steps it takes during the validation/release process.