To install rbenv-each, clone this repository into your rbenv plugins directory. (You'll need a recent version of rbenv that supports plugin bundles.)
$ mkdir -p "$(rbenv root)"/plugins
$ git clone https://github.com/chriseppstein/rbenv-each.git "$(rbenv root)"/plugins/rbenv-each
$ rbenv help each
Verbose mode will print a header for each ruby so you can distinguish the output.
$ rbenv each bundle install
$ rbenv each -v rake test