While working on remirror I always intended to setup a local npm registry for testing the packages before being published.
In the end I didn't get to do this but I would like to implement something like this functionality as a builtin feature for monots.
So many things can go wrong while publishing a new package, and it's a great idea to make sure the CI system catches the errors before the end users do.
Here's a sample repo on how these e2e tests can be setup and run. And here's a video describing what is being done.