Factory Girl Automatic Tests

Introduction
Early in a project I started to use factory girl without fully understanding it.  After many months of creating steps like "Given /^(\d+) blog exists$/" and "Given /^the following blogs exist:$/" I started to come up with generic functions that would build those steps.

Stupid me for not checking that factory girl already does something like that.  All you have to do is include factory girl's step_definitions.rb file:

requie 'factory_girl/step_definitions'

view raw env.rb hosted with ❤ by GitHub

Once you start using FactoryGirl correctly there are a world of new features that can make your steps both cleaner and more concise.  Here are some tips I have found via trial and error.

Tip 1: Do not reinvent the wheel
Factory girl will create steps for all factories that you have register.

	Scenario: Showing example steps
	Given the following blogs exist:
	| name |
	| first blog |
	Given a blog exists with a name of "first blog"
	Given a blog exists
	Given 41 blogs exist
	Given 14 blogs exist with a description of "Test"

view raw example_steps.feature hosted with ❤ by GitHub

Tip 2: Use association, Do not add more steps then are needed
Factory girl association are automatically created before the factory is created and they are automatically linked.  It only supports the belongs_to behavior, so keep that in mind.

Using the "Given the following XXX exist" step you can define attributes, on the the association, in the table.  If we leave the association out then a default is created.  If we define an attribute then it will be found or created using that attribute.

Lets say you have a product and it can belog to a category.  You do not need to create a category.

	class Category < ActiveRecord::Base
	end
	class Product < ActiveRecord::Base
	belongs_to :category
	end
	FactoryGirl.define do
	factory :category do
	name 'Foo'
	end
	factory :product do
	association :category
	name 'Bar'
	end
	end

view raw product_category.rb hosted with ❤ by GitHub

	Scenario: Bad
	Given a category exists with a name of "Foo"
	Given a product exists with a category of "Foo"
	Scenario: Good
	Given the following products exist:
	| name | category |
	| Foo | name: Bar |

view raw product_category.feature hosted with ❤ by GitHub

Tip 3: Attaching files via CarrierWave
Since cucumber is a text file it doesn't make much sense for you to define full files in steps.  It also doesn't really make sense to embed full file paths in the tests.  Instead, you can use a Transient attribute and some code so that in cucumber you define a file name and in the factory it converts to an actual file.

	class Product < ActiveRecord::Base
	mount_uploader :file, FileUploader
	end
	FactoryGirl.define do
	factory :product do
	ignore do
	file_name 'small_image.png'
	end
	file { File.open(Rails.root.join("path/to/files",file_name)) unless file_name.blank? }
	end
	end

view raw file_product.rb hosted with ❤ by GitHub

	Scenario: Products
	Given a product exists
	# 1 product with an included file whose file_name was "small_image.png"
	Given the following products exist:
	| name | file name |
	| No image | |
	| Big image | big_image.png |

view raw file_product.feature hosted with ❤ by GitHub

Tip 4: Fixing a circular dependency between two models
Lets say you have a Store model and User model.  And a User can both work at and own a Store.  If you put associations in both the User and the Store model then each will try to create the other, infinitely.  We can reuse the transient method as before to break the circle.

The trick is to avoid defining an association in both factories, but instead use a transient attribute in one factory to simulate the behavior of an association.  Also, since transient attributes are not likely to have the same level of sophistication as the associations you should use the association to define the more complex of the two models.

	class User < ActiveRecord::Base
	belongs_to :store
	has_many :stores, :foreign_key => 'owner_id'
	end
	class Store < ActiveRecord::Base
	belongs_to :owner, :class_name => 'User'
	end
	FactoryGirl.define do
	factory :user do
	name 'John Doe'
	ignore do
	store_name nil
	end
	store {Store.find_or_create_by_name(store_name || 'Test store')}
	end
	factory :store do
	name 'Test store'
	association :owner, :factory => :user
	end
	end

view raw user_store.rb hosted with ❤ by GitHub

	Scenario: 2 users named 'John Doe', and 2 stores named "Test store"
	Given a user exists
	Given a store exists
	Scenario: 2 users both working at the same store
	Given the following users exist:
	| name | store name |
	| John Doe | Test store |
	| Jane Doe | Test store |
	Scenario: 2 stores both owned by the same person
	Given the following stores exist:
	| name | owner |
	| MD Store | name: John Doe |
	| CA Store | name: John Doe |

view raw user_store.feature hosted with ❤ by GitHub

Tip 5: Fixing a circular dependency between the same model
Let say you have a Category model, and that model can belong to another Category (a tree) then you cannot use an association or you get the same infinite recursion issue as before.  Here we can use a transient attribute along with an after_create hook to simulate the behavior we want.

	class Category < ActiveRecord::Base
	acts_as_nested_set
	end
	FactoryGirl.define do
	factory :category do
	name 'Foo'
	ignore do
	parent nil
	end
	after_create do |category,attributes|
	unless attributes.parent.blank?
	parent = Category.find_by_name(attributes.parent)
	category.move_to_child_of(parent)
	end
	end
	end
	end

view raw category.rb hosted with ❤ by GitHub

	Scenario: Has no parents
	Given the following categories exist:
	| name |
	| Foo |
	| Bar |
	| Baz |
	Scenario: Nested tree
	Given the following categories exist:
	| name | parent |
	| Foo | |
	| Bar | Foo |
	| Baz | Bar |
	# + Foo
	# |+ Bar
	# |- Baz

view raw category.feature hosted with ❤ by GitHub