isotope|eleven

Define a controller with an infinite loop and start up a rails server.

class SomeController < ApplicationController
  def show
    while true do
    end
  end
end

Make a request to /home/any-params to call the show method. Then find the location of the ruby executable, and the PID of the running process.

$ which ruby
/usr/bin/ruby
$ top
  PID   USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
  25215 ben       20   0 40100  27m 2088 R  100  0.9   0:15.53 ruby

Attach a GDB session to the ruby process.

$ gdb /usr/bin/ruby 25215

Call the rb_backtrace() function from within GDB.

(gdb) call rb_backtrace()

Check the passenger log.

from /home/ben/rails/app/controllers/some_controller.rb:3:in `show'
...

You can also raise an exception.

(gdb) call rb_raise((int)rb_eException, "Raised a special exception with GDB")

Check the production log.

Exception (Raised a special exception with GDB):
  app/controllers/some_controller.rb:3:in `show'

I wrote some Rspec tests for our recent release of the state_machine_audits gem, and thought I'd share the steps I took to add Rspec tests. To get started, I had to get the code and update the gemspec.

Setting up the .gemspec

The git repository containing the source code can be found on Github or by clicking the "Source Code" link on RubyGems.org. I used the command git clone git://github.com/isotope11/state_machine_audits.git to clone the repository into a folder called state_machine_audits in the present working directory. Before I could start adding Rspec tests, I had to add rspec and sqlite3 to the development dependencies under Gem::Specification.

# in state_machine_audits.gemspec
Gem::Specification.new do |s|
  # ...
  s.add_development_dependency 'rspec', '~> 2.4.0'
  s.add_development_dependency 'sqlite3', '~> 1.3.3'
end

Adding Rspec tests

After installing the rspec gem and requiring the libraries used by state_machine_audits, I used ActiveRecord to create a sqlite3 database in memory and ran migrations against that database:

    # in spec/state_machine_audits_spec.rb
require 'active_record'
require 'active_support'
require 'state_machine'
require 'state_machine_audits'

ActiveRecord::Base.establish_connection(:adapter => "sqlite3", :database => ":memory:")

ActiveRecord::Base.connection.create_table(:state_machine_state_audits) do |t|
  t.string :state_machine_auditable_type
  t.integer :state_machine_auditable_id
  t.string :state_field
  t.string :state
  t.timestamps
end

Next, I added a generic Vehicle model with migrations and an ignite event to use the state_machine gem:

# in spec/state_machine_audits_spec.rb
class Vehicle < ActiveRecord::Base
  include StateMachineAudits

  state_machine :initial => :parked do
    event :ignite do
      transition :parked => :first_gear
    end
  end
end

Finally, I used the Rspec describe syntax to test that audits were being added to the database after state changes. To run the tests, I used bundle exec rspec spec/ to make sure the tests were run against the version specified in the gemspec. The only thing left was to update the version and push the changes to RubyGems.

Changing versions and pushing changes

Updating the version was simple -- I just modified the file lib/state_machine_audits/version.rb. After Josh added my RubyGems account to the permissions, I used the command gem build in the gem's root directory to generate a new gem file, and gem push state_machine_audits-0.1.1.gem to update the RubyGems version. That's it! Oh, and if you are contributing to gem development, don't forget to add yourself to the authors before you push ;)