Shoulda Macros with Blocks

David Eisinger, Development Director

Article Category: #Code

Posted on

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.


David Eisinger

David is Viget's managing development director. From our Durham, NC, office, he builds high-quality, forward-thinking software for PUMA, the World Wildlife Fund, NFLPA, and many others.

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