GIANT ROBOTS SMASHING INTO OTHER GIANT ROBOTS

Factory Girl now has callbacks thanks to Nate Sutton (a.k.a. fowlduck).

There are three callbacks respectively called after Factory methods you already know:

These come in handy in a number of common use cases.

Basic has many associations

Models:

class Article < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :article
end

Factories:

Factory.define :article do |article|
  article.body { "password" }
end

Factory.define :comment do |comment|
  comment.body { 'Great article!' }
end

Factory.define :article_with_comment, :parent => :article do |article|
  article.after_create { |a| Factory(:comment, :article => a) }
end

Nice. Callbacks let us do this:

article = Factory(:article_with_comment)

Instead of this:

article = Factory(:article)
comment = Factory(:comment, :article => article)

Polymorphic relationships

The savings get larger when the object graph gets more complex:

Models:

class User < ActiveRecord::Base
  has_many :interests, :as      => :interested
  has_many :topics,    :through => :interests
end

class Interest < ActiveRecord::Base
  belongs_to :topic
  belongs_to :interested, :polymorphic => true
end

Building block factories:

Factory.define :user do |user|
  user.email                 { Factory.next(:email) }
  user.password              { "password"   }
  user.password_confirmation { "password"   }
end

Factory.define :email_confirmed_user, :parent => :user do |user|
  user.email_confirmed { true }
end

Factory.define :topic do |topic|
  topic.name {'topic_name'}
end

Factory.define :interest do |interest|
  interest.association(:topic)
  interest.interested { |i| i.association(:user) }
end

Factory.define :music_interest, :class => 'Interest' do |interest|
  interest.topic { |topic| topic.association(:topic, :name => "Music") }
end

Factory.define :sports_interest, :class => 'Interest' do |interest|
  interest.topic { |topic| topic.association(:topic, :name => "Sports") }
end

And now the payoff:

Factory.define :musical_user, :parent => :email_confirmed_user do |user|
  user.after_create { |u| Factory(:music_interest, :interested => u) }
end

Factory.define :sporty_user, :parent => :email_confirmed_user do |user|
  user.after_create { |u| Factory(:sports_interest, :interested => u) }
end

Again, factories let us do this:

user = Factory(:musical_user)

Instead of:

user = Factory(:email_confirmed_user)
Factory(:music_interest, :interested => user)

More intention-revealing. More encapsulation, protecting us from change.

Working with fakes

If you haven’t read it, read “Have you ever… faked it?”. We’re finding this to be a good approach for testing objects that interface with web services such as geocoding and payment processing.

class User < ActiveRecord::Base
  acts_as_mappable
  before_validation :geocode_location, :if => :location_changed?

  def geocode_location
    geo = Geokit::Geocoders::MultiGeocoder.geocode(location)
    self.lat, self.lng = geo.lat, geo.lng
  end
end

Factory.define :boston_user, :parent => :email_confirmed_user do |user|
  user.location { "Boston, MA" }

  user.after_build { |u|
    Geokit::Geocoders::FakeGeocoder.locations["Boston, MA"] = [0, 1]
  }
end

Enjoy!

Get version 1.2.3 with callbacks on Gemcutter:

sudo gem install factory_girl -s http://gemcutter.org

Happy testing.