FactoryGirl and polymorphic associations

Question

The design

I have a User model that belongs to a profile through a polymorphic association. The reason I chose this design can be found here. To summarize, there are many users of the application that have really different profiles.

class User < ActiveRecord::Base
  belongs_to :profile, :dependent => :destroy, :polymorphic => true
end

---

class Artist < ActiveRecord::Base
  has_one :user, :as => :profile
end

---

class Musician < ActiveRecord::Base
  has_one :user, :as => :profile
end

After choosing this design, I'm having a hard time coming up with good tests. Using FactoryGirl and RSpec, I'm not sure how to declare the association the most efficient way.

First attempt

factories.rb

Factory.define :user do |f|
  # ... attributes on the user
  # this creates a dependency on the artist factory
  f.association :profile, :factory => :artist 
end

Factory.define :artist do |a|
  # ... attributes for the artist profile
end

user_spec.rb

it "should destroy a users profile when the user is destroyed" do
  # using the class Artist seems wrong to me, what if I change my factories?
  user = Factory(:user)
  profile = user.profile
  lambda { 
    user.destroy
  }.should change(Artist, :count).by(-1)
end

Comments / other thoughts

As mentioned in the comments in the user spec, using Artist seems brittle. What if my factories change in the future?

Maybe I should use factory_girl callbacks and define an "artist user" and "musician user"? All input is appreciated.

Answer 1

Although there is an accepted answer, here is some code using the new syntax which worked for me and might be useful to someone else.

spec/factories.rb

FactoryGirl.define do

  factory :musical_user, class: "User" do
    association :profile, factory: :musician
    #attributes for user
  end

  factory :artist_user, class: "User" do
    association :profile, factory: :artist
    #attributes for user
  end

  factory :artist do
    #attributes for artist
  end

  factory :musician do
    #attributes for musician
  end
end

spec/models/artist_spec.rb

before(:each) do
  @artist = FactoryGirl.create(:artist_user)
end

Which will create the artist instance as well as the user instance. So you can call:

@artist.profile

to get the Artist instance.