Gem dev workflow?

I am beginning development of my first Gem for a Rails app. I am
curious what some best practices are regarding development workflow.

As the Gem will be Rails dependent, it seems as though it needs to be
vendored so that I can easily run tests, write code and see changes
during development instead of rebuilding and reinstalling the gem
hundreds of times daily.

I was thinking that a good way to handle this would be to have the Gem
structure live in the context of a "development only" Rails app, and
that all files except the Gem files would be added to .gitignore.

But as I have yet to build a Rails dependent Gem, I don't know what
the preferred way to do this is.

How do you guys handle Gem dev workflow?

Thanks, Elliott G