On testing rake files

I started to be concerned about how to test Rake files just recently.

There was an issue for one of the gems I wrote. The gem is mostly a bunch of Rake tasks.

Here’s an example of such a task:

  task :create do
    rakefile = File.expand_path('Rakefile', dummy_path)
    command = "rake -f '%s' db:create" % rakefile
    sh(command) unless ENV["DISABLE_CREATE"]
  end

Now following the articles from Thoughtbot and Tyler, and learning how I could write my tests, I tried to put together hopefully the best of both approaches into a gem I could reuse.

I wrote RSpec Rake, which should provide two important things that could help write rake tests easily:

• A specific RSpec Example Group with relevant task initialization and hooks
• Metadata integration to allow flexible declaration of tasks location or Rake file name

Now using rspec-rake, here’s an example test for the task from above:

# spec/tasks/dummy_create_spec.rb

require 'spec_helper'

describe 'dummy:create' do
  it 'calls rake with db:create task' do
    rakefile = File.expand_path('../../dummy/Rakefile', __FILE__)
    command = "rake -f '%s' db:create" % rakefile
    # An equivalent of mocking `sh` method
    Rake::AltSystem.should_receive(:system).with(command).and_return(true)
    task.invoke
  end
end

Hopefully this will motivate others to write more Rake task tests too.
For more documentation check the Github repository.