irb & script/console tips

Dan Croak

Let’s get interactive. You can learn a lot about your application from irb and by extension, script/console.

Wirble: colors

Color matters. You’re picky about your text editor syntax highlighting and maybe you use the excellent redgreen gem for colors in your test backtraces. Gotta have it in irb, too.

First, install Wirble:

sudo gem install wirble

Then, in your ~/.irbrc:

require 'rubygems'
require 'wirble'

Wirble: history

Wirble has an added bonus: history.

irb(main):001:0> history = "History?"
=> "History?"
irb(main):002:0> exit

Without Wirble, if you drop back into irb, you can’t arrow up to your previous commands. With Wirble, you can.

Wirble: auto-completion

As if that’s not enough, Wirble gives you auto-completion, too. In irb:

>> un_momento = "Spanish for like, 'hold the phone!'"
=> "Spanish for like, 'hold the phone!'"

Type, un, then tab:

>> un
un_momento   undef        unless       untaint      untrace_var  until

Local methods

Stick this in your ~/.irbrc:

# Easily print methods local to an object's class
class Object
  def local_methods
    (methods - Object.instance_methods).sort

Use the local_methods method like this:

>> class BasketballPlayer
>>   attr_accessor :name
?>   def champion?
>>     name == "Kevin Garnett"
>>   end
>> end
=> nil
>> kevin_garnett =
=> #<BasketballPlayer:0x11988f8>
>> = "Kevin Garnett"
=> "Kevin Garnett"
>> kevin_garnett.champion?
=> true
>> kevin_garnett.local_methods
=> ["champion?", "name", "name="]


Don’t forget you can alias in irb. The only one I have is:

alias q exit

It makes irb feel more Vim-ish.

Create test fixtures for a third party service

Your app uses the Flickr API. You want your test suite to use legitimate data but not hit the service.

Given the actual call to the service is:"Bruce Springsteen")

Run the query in script/console and convert the data into yaml:

yaml ="Bruce Springsteen").to_yaml

Then use your old Ruby friend, with the write option (w) to dump it to a file:"test/fixtures/flickr/springsteen.yml", "w") { |file| file << yaml }

Add this to your test_helper.rb:

def load_yaml_fixture(path)
  absolute_path = File.join(RAILS_ROOT, "test", "fixtures", path)
  YAML::load_file absolute_path

Voila, when you need to mock out calls to the third party service, you can now use this in your test code:


This pattern is repeatable for any third party service. Just replace the actual call with whatever you’re working on, and name the fixture something intention-revealing.

Oftentimes script/console is used for debugging, and what better way to do that than to get the SQL generated by each method call. Stick this in your ~/.irbrc:

# Log to STDOUT if in Rails
if ENV.include?('RAILS_ENV') && !Object.const_defined?('RAILS_DEFAULT_LOGGER')
  require 'logger'

This gets you:

>> videos =
  Video Load (0.4ms)   SELECT * FROM `videos` LIMIT 3
=> [#<Video id: 1, ...>]

Without the ~/.irbrc love, you’d be missing:

Video Load (0.4ms)   SELECT * FROM `videos` LIMIT 3


After you’ve required rubygems for Wirble, require pretty print, too:

require 'pp'

This is just a nice way to have better formatting at your fingertips. It’s especially helpful when dealing with an Array of ActiveRecord objects:

>> pp videos
[#<Video id: 1, youtube_id: "TcMklv40YMY", name: "Merb, Rubinius and the
Engine Yard Stack", upload_time: nil, view_count: 6171, description: "Google
Tech Talks\nOctober 20, 2008\n\nABSTRACT\n\nIn th...", created_at: "2008-12-21
00:32:33", updated_at: "2008-12-21 00:32:33">, #<Video id: 2, youtube_id:
"JySmT-dGOj0", name: "MERB SPORTS Team-Vorstellung 2008", upload_time: nil,
view_count: 495, description: "MERB SPORTS stellt sich für die VDRM-Saison 2008
v...", created_at: "2008-12-21 00:32:33", updated_at: "2008-12-21 00:32:33">,
#<Video id: 3, youtube_id: "6bc-FNNWIsM", name: "Merb && Moi", upload_time:
nil, view_count: 58, description: "Amusing yes?", created_at: "2008-12-21
00:32:33", updated_at: "2008-12-21 00:32:33">]