Spring
Spring is a Rails application preloader. It speeds up development by keeping your application running in the background so you don't need to boot it every time you run a test, rake task or migration.
(from https://github.com/rails/spring)
How to setup Spring
bundle exec spring binstub rspec
# then
bundle exec rails s -p 3001
Check if it's working
$ bundle exec spring status
Spring is running:
2780 spring server | AppName | started 1 min ago
Enjoy.