David Eisinger

Elsewhere > Shoulda Macros with Blocks

Posted 2009-04-29 on viget.com

When I’m not working on client projects, I keep myself busy with SpeakerRate, a site that lets conference goers rate the talks they’ve attended. After a number of similar suggestions from users, we decided to display the total number of ratings alongside the averages. Although only talks can be rated, speakers, events and series also have ratings through their associated talks. As you can imagine, calculating the total ratings for each of these required a lot of somewhat repetitive code in the models, and very repetitive code in the associated tests.

Fortunately, since we’re using Shoulda, we were able to DRY things up considerably with a macro:

class Test::Unit::TestCase
  def self.should_sum_total_ratings
    klass = model_class

    context "finding total ratings" do
      setup do
        @ratable = Factory(klass.to_s.downcase)
      end

      should "have zero total ratings if no rated talks" do
        assert_equal 0, @ratable.total_ratings
      end

      should "have one total rating if one delivery & content rating" do
        talk = block_given? ? yield(@ratable) : @ratable
        Factory(:content_rating, :talk => talk)
        Factory(:delivery_rating, :talk => talk)

        assert_equal 1, @ratable.reload.total_ratings
      end
    end
  end
end

This way, if we’re testing a talk, we can just say:

class TalkTest < Test::Unit::TestCase
  context "A Talk" do
    should_sum_total_ratings
  end
end

But if we’re testing something that has a relationship with multiple talks, our macro accepts a block that serves as a factory to create a talk with the appropriate relationship. For events, we can do something like:

class EventTest < Test::Unit::TestCase
  context "An Event" do
    should_sum_total_ratings do |event|
      Factory(:talk, :event => event)
    end
  end
end

I’m pretty happy with this solution, but having to type “event” three times still seems a little verbose. If you’ve got any suggestions for refactoring, let us know in the comments.