FactoryGirl with polymorphic associations

polymorphic_factory.rb

# a common polymorphic model
class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
end

class Article < ActiveRecord::Base
  has_many :comments, as: :commentable, dependent: :destroy
end

class Collection < ActiveRecord::Base
  has_many :comments, as: :commentable, dependent: :destroy
end

# this is how you can build your factories in FactoryGirl
# to deal with the polymorphic association
FactoryGirl.define do
  factory :article_comment, class: "Comment" do
    association :commentable, factory: :article
    # other attributes for slideshow model
  end
  
  factory :collection_comment, class: "Comment" do
    association :commentable, factory: :collection
    # other attributes for article model
  end
end