Notes: Emacs, Rails, Rspec

Running Ruby tests using Emacs’ rspec-mode and the Zeus Rails preloader.

Use cases:

  1. Switch between a Ruby file and its test.
  2. Run the test of the current file (or the test itself).

A few plugins will do this out of the box (rinari?) but this was the simplest.


  • Emacs, duh.
  • rbenv and some version of Ruby.
  • Zeus and Rspec (gem install zeus rspec)
  • rspec-mode (M-x package-install)


Emacs needs to know where the rbenv shims are located. Add this to Emacs initialization.

(setenv "PATH"
       (getenv "HOME") "/.rbenv/shims:"
       (getenv "HOME") "/.rbenv/bin:"
       (getenv "PATH")))
(setq exec-path
    (cons (concat
           (getenv "HOME") "/.rbenv/shims")
           (cons (concat (getenv "HOME") "/.rbenv/bin") exec-path)))

Also, a simpler rspec-mode prefix makes things easier to use.

 ;; ... other stuff ...
 `(rspec-key-command-prefix (kbd "M-s")))


Start up a Zeus instance and you’re good to go.

  • Switch to (or from) test: M-s t
  • Run test: M-s v
  • Run suite: M-s a

Bonus Points

Some Rails installations use engines, many of which include separate spec folders for each engine.

When rspec-mode runs a test it looks for a Zeus socket to use. The socket (.zeus.sock) typically appears in the Rails root. rspec-mode shortcuts knowing where that is and just uses ../#{spec_root}. In an engine-specific test, ../#{spec_root} is actually the engine root so there won’t be a socket available.

The “fix” is to symlink the socket to wherever you need it. Quick and dirty.

cd rails_root/
ln -s .zeus.sock engines/frontend/.zeus.sock
ln -s .zeus.sock engines/backend/.zeus.sock
# ... etc ...

2015-04-14: Fixed wrong ruby-build URL