Rocksteady¶ ↑

Often you need to test bits of code you write with bits of code other people write, across varying revisions. This is tedious, requiring a lot of custom work and infrastructure, so you probably don’t do it enough. I know I don’t, and it’s a bad habit.

Rocksteady is meant to ease the process of switching out different versions of inter-dependent code, providing you with a simple scenario metaphor to write build and test code within. It’s test framework agnostic (it just uses exit codes), and extremely flexible.

Below you can read an example of testing different versions of Rails against different versions of a plugin; more in-depth examples can be found on the wiki (github.com/bruce/rocksteady/wikis/examples).

Please let me know how you’re using Rocksteady; it’s nice to have feedback.

Bruce Williams (codefluency.com) github.com/bruce

Get it from RubyForge (once released):

sudo gem install rocksteady

• rake

  sudo gem install rake
  

• ruport

  sudo gem install ruport
  

• mojombo-grit >= 0.8.0

  sudo gem install mojombo-grit -s http://gems.github.com

• (git in your PATH)

Create a new directory, and toss a Rakefile in it. Make it look like this:

require 'rubygems'
require 'rocksteady'

Now, point it at the (bare) git repos that are holding the code you’d like to test. You could clone the repos somewhere in this directory, if you’d like. For this example, we’ll be testing a Rails plugin we’ve written against various versions of Rails, so it like look something like this (assuming we cloned bare .git repos into the current directory)

repos 'rails.git', 'our_plugin.git'

Okay, now let just create a single scenario. In general, a scenario will be some set of configuration you’d like to test. For this example we won’t be doing anything fancy (just a simple drop in vendor/plugins) so it might look like this:

scenario "Installed in vendor/plugins" do
  generate_rails_app
  install_plugin
  verify_loads_environment
end

You see 3 things need to happen in the scenario; we’ve broken these out for clarity and just define them underneath.

First, let’s generate a fresh Rails app for testing with:

def generate_rails_app
  ruby "#{rails_path}/railties/bin/rails rails_app"
  cp_r rails_path, 'rails_app/vendor/rails'
end

A few notes on what you see above:

1. ruby is simply a rake convenience method that calls out to a new ruby interpreter

2. rails_path is the absolute path to a fresh clone of the rails.git repo we defined at the beginning of the file, checked-out to the reference point we’re currently checking (more on how that’s set later). *_path convenience methods are generated for all the repos you’ve defined; you’ll see the other one in install_plugin.

3. First we’re calling out to the rails executable in the checked-out source directly so we can generate an accurate skeleton app for that version. The rails_app argument is just the name of the directory where it will be generated. Finally, we’re copying Rails into vendor/rails so this copy overrides any gems installed on our system.

It’s worth noting that when scenarios are being run, the current working directory is changed for you automatically; right now you’re actually sitting in build/<timestamp>/scenarios/installed_in_vendor_plugins, where rails_app will be generated as a subdirectory.

Let’s install the plugin now:

def install_plugin
  cp_r our_plugin_path, 'rails_app/vendor/plugins'
end

1. cp_r is another rake convenience method that does a recursive copy.

2. our_plugin_path is the *_path method generated automatically for our plugin repo.

So, that was simple; for this quick example we just copy the plugin directly in.

Now let’s do something that just verifies the Rails app code will load successfully across the standard environments, just by printing the Rails version from script/runner:

def verify_loads_environment
  Dir.chdir 'rails_app' do
    %w(test development production).each do |env|
      ENV['RAILS_ENV'] = env
      ruby "script/runner 'p Rails::VERSION'"
    end
  end
end

The great thing about the convenience methods that rake provides (eg, ruby, sh, cp_r, etc) is that the raise an exception if the system call they make returns a bad exit code; the scenario automatically catches them and assigns a failure to the scenario. If you’re not using these convenience methods and need to assign a failure, you can raise an exception manually to get the same result.

Note that your scenario should return a true-ish value or else it will get run multiple times. (This is because the result of the scenario is memoized for later reference.) Rocksteady judges the success of a scenario based on whether it runs to completion or not. If you want your scenario to fail, just raise an exception or let one bubble out of steps inside your scenario.

Here are some examples on how we could run the scenario, with plain English explanations:

Run all scenarios, with all repos set to master:

$ rake rocksteady

Run just the first scenario (you can use rake -T to see them all), with all repos set to master:

$ rake rocksteady:scenario:1

The same, but setting rails to v2.0.2:

$ rake rocksteady:scenario:1 REFS=rails:v2.0.2

and now with our_plugin set to the experimental branch:

$ rake rocksteady:scenario:1 REFS=rails:v2.0.2,our_plugin:experimental

You can also use full references:

$ rake rocksteady:scenario:1 REFS=rails:refs/tags/v2.0.2,our_plugin:refs/heads/experimental

Currently the output is a simple text-based table. You’ll need to refer to the output in the terminal to find where your failures occur. More granular, labelled scenario-level logging is on the roadmap.

Copyright (c) 2008 Bruce R. Williams

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