How to tell which version of a gem a rails app is using

Question

I\'m investigating a rails app - the prod server has two version of a specific gem installed, how can I tell which version the prod app is using?

Answer 1

There's also a list in Gemfile.lock, located in the root directory of your app.

For this reason I leave Gemfile.lock out of my .gitignore. This has saved me more than once when I forgot to specify the gem version in GemFile, and a gem got updated with breaking changes.