We all know the problem: different developers prefer different libraries, especially for their development workflow. However, for various reasons we may not just want to add them unconditionally to our application’s Gemfile: Added dependencies (including their own dependencies) for something that doesn’t directly relate to the actual app. Bikeshedding discussions about the virtue of gem A over gem B or why we should never use gem C 🙄 For this reason I generally add a Gemfile.