Tired of upgrading to the latest Ruby version every new year? Just have the latest Ruby version already running! Ruby head is the latest commit to the main branch of Ruby on Github. It’s dangerous to run our Rails app on Ruby head, but we can run Ruby head on application tests. We'll build Ruby head on a Docker image and run it with tests on Buildkite. Along the way, we'll learn about using Docker, jemalloc (an an alternate malloc implementation) and why it's important to your team and the Ruby community to do this work.