FactoryGirl Polymorphic Association

gistfile1.rb

class Alert < ActiveRecord::Base
  belongs_to :alertable, :polymorphic => true
end


class Region < ActiveRecord::Base
  has_many :alerts, :as => :alertable
end


FactoryGirl.define do
  Factory.define :alert do |alert|
    alert.alertable { |a| a.association(:region) }
  end
end

There is the fix form factory_bot documents

Polymorphic associations can be handled with traits:

FactoryBot.define do
  factory :video
  factory :photo

  factory :comment do
    for_photo

    trait :for_video do
      association(:commentable, factory: :video)
    end

    trait :for_photo do
      association(:commentable, factory: :photo)
    end
  end
end

This allows us to do:

create(:comment)
create(:comment, :for_video)
create(:comment, :for_photo)