How to dry-run publishing a release?

[elalish]

I just found Act because I'm driven up the wall by my Github release actions. My CI is fine - it runs all the time, so problems are quick to correct. However, the workflows that only run on release, e.g. to publish packages to PyPI and npm, only run maybe every couple of months. That turns out to be long enough that all the actions we depend on have made changes to keep up with Github's changes and nothing works from version mismatches.

Act seems like a great option, but how do we try out a publishing workflow without actually publishing? Offline mode sounds like it might help - is there a way to set it up to be online for updating caches (download) but offline for upload to ensure nothing is actually published? Or is there a better way to set this up?