Singleton factories in factory_girl/machinist?

Question

Is there some configuration in a factory of factory girl/machinist that forces it to create objects with the same factory name just once during test case and return the same instance all the time? I know, i can do something like:

def singleton name
    @@singletons ||= {}
    @@singletons[name] ||= Factory name
end
...
Factory.define :my_model do |m|
   m.singleton_model { singleton :singleton_model }
end

but maybe there is a better way.

Schoolbook

Answer 1

You can use the initialize_with macro inside your factory and check to see if the object already exists, then don't create it over again. This also works when said factory is referenced by associations:

FactoryGirl.define do
  factory :league, :aliases => [:euro_cup] do
    id 1
    name "European Championship"
    owner "UEFA"
    initialize_with { League.find_or_create_by_id(id)}
  end
end

There is a similar question here with more alternatives: Using factory_girl in Rails with associations that have unique constraints. Getting duplicate errors

Busy

With Rails 4, you'll want to use League.where(:id => id).first_or_create -- If you have a before_save that requires information to be set, then you may want find_or_initialize_by_id or first_or_initialize – Mirabella

Answer 2

@CubaLibre answer with version 5 of FactoryBot:

FactoryGirl.define do
  factory :league do
    initialize_with { League.find_or_initialize_by(id: id) }
    sequence(:id)
    name "European Championship"
  end
end

Orientalize

Answer 3

Not sure if this could be useful to you.

With this setup you can create n products using the factory 'singleton_product'. All those products will have same platform (i.e. platform 'FooBar').

factory :platform do
  name 'Test Platform'
end

factory :product do
  name 'Test Product'
  platform

  trait :singleton do
    platform{
      search = Platform.find_by_name('FooBar')
      if search.blank?
        FactoryGirl.create(:platform, :name => 'FooBar')
      else
        search
      end
    }
  end

  factory :singleton_product, :traits => [:singleton]
end

You can still use the standard product factory 'product' to create a product with platform 'Test Platform', but it will fail when you call it to create the 2nd product (if platform name is set to be unique).

Elwoodelwyn

More detailed answer in this topic, including a more thorough explanation of the above, plus an alternative solution if you are using Cucumber: #2015973 – Elwoodelwyn