Getting Started
Update Your Gemfile
If you're using Rails, you'll need to change the required version of factory_girl_rails:
gem "factory_girl_rails", "~> 1.2"
If you're not using Rails, you'll just have to change the required version of factory_girl:
gem "factory_girl", "~> 2.1.0"
Once your Gemfile is updated, you'll want to update your bundle.
Defining factories
Each factory has a name and a set of attributes. The name is used to guess the class of the object by default, but it's possible to explicitly specify it:
# This will guess the User class
FactoryGirl.define do
factory :user do
first_name 'John'
last_name 'Doe'
admin false
end
# This will use the User class (Admin would have been guessed)
factory :admin, :class => User do
first_name 'Admin'
last_name 'User'
admin true
end
# The same, but using a string instead of class constant
factory :admin, :class => 'user' do
first_name 'Admin'
last_name 'User'
admin true
end
end
It is highly recommended that you have one factory for each class that provides the simplest set of attributes necessary to create an instance of that class. If you're creating ActiveRecord objects, that means that you should only provide attributes that are required through validations and that do not have defaults. Other factories can be created through inheritance to cover common scenarios for each class.
Attempting to define multiple factories with the same name will raise an error.
Factories can be defined anywhere, but will be automatically loaded if they are defined in files at the following locations:
test/factories.rb
spec/factories.rb
test/factories/*.rb
spec/factories/*.rb
Using factories
factory_girl supports several different build strategies: build, create, attributes_for and stub:
# Returns a User instance that's not saved
user = FactoryGirl.build(:user)
# Returns a saved User instance
user = FactoryGirl.create(:user)
# Returns a hash of attributes that can be used to build a User instance
attrs = FactoryGirl.attributes_for(:user)
# Returns an object with all defined attributes stubbed out
stub = FactoryGirl.build_stubbed(:user)
# Passing a block to any of the methods above will yield the return object
FactoryGirl.create(:user) do |user|
user.posts.create(attributes_for(:post))
end
No matter which strategy is used, it's possible to override the defined attributes by passing a hash:
# Build a User instance and override the first_name property
user = FactoryGirl.build(:user, :first_name => 'Joe')
user.first_name
# => "Joe"
If repeating "FactoryGirl" is too verbose for you, you can mix the syntax methods in:
# rspec
RSpec.configure do |config|
config.include FactoryGirl::Syntax::Methods
end
# Test::Unit
class Test::Unit::TestCase
include Factory::Syntax::Methods
end
This would allow you to write:
describe User, "#full_name" do
subject { create(:user, :first_name => "John", :last_name => "Doe") }
its(:full_name) { should == "John Doe" }
end
Lazy Attributes
Most factory attributes can be added using static values that are evaluated when the factory is defined, but some attributes (such as associations and other attributes that must be dynamically generated) will need values assigned each time an instance is generated. These "lazy" attributes can be added by passing a block instead of a parameter:
factory :user do
# ...
activation_code { User.generate_activation_code }
date_of_birth { 21.years.ago }
end
Aliases
Aliases allow you to use named associations more easily.
factory :user, :aliases => [:author, :commenter] do
first_name "John"
last_name "Doe"
date_of_birth { 18.years.ago }
end
factory :post do
# instead of
# association :author, :factory => :user
title "How to read a book effectively"
body "There are five steps involved."
end
factory :comment do
commenter
# instead of
# association :commenter, :factory => :user
body "Great article!"
end
Dependent Attributes
Attributes can be based on the values of other attributes using the proxy that is yielded to lazy attribute blocks:
factory :user do
first_name 'Joe'
last_name 'Blow'
email { "#{first_name}.#{last_name}@example.com".downcase }
end
FactoryGirl.create(:user, :last_name => 'Doe').email
# => "[email protected]"
Transient Attributes
There may be times where your code can be DRYed up by passing in transient attributes to factories.
factory :user do
ignore do
rockstar true
upcased { false }
end
name { "John Doe#{" - Rockstar" if rockstar}" }
email { "#{name.downcase}@example.com" }
after_create do |user, proxy|
user.name.upcase! if proxy.upcased
end
end
FactoryGirl.create(:user, :upcased => true).name
#=> "JOHN DOE - ROCKSTAR"
Static and dynamic attributes can be ignored. Ignored attributes will be ignored within attributes_for and won't be set on the model, even if the attribute exists or you attempt to override it.
Within Factory Girl's dynamic attributes, you can access ignored attributes as you would expect. If you need to access the proxy in a Factory Girl callback, you'll need to declare a second block argument (for the proxy) and access ignored attributes from there.
Associations
It's possible to set up associations within factories. If the factory name is the same as the association name, the factory name can be left out.
factory :post do
# ...
end
You can also specify a different factory or override attributes:
factory :post do
# ...
association :author, :factory => :user, :last_name => 'Writely'
end
The behavior of the association method varies depending on the build strategy used for the parent object.
# Builds and saves a User and a Post
post = FactoryGirl.create(:post)
post.new_record? # => false
post..new_record? # => false
# Builds and saves a User, and then builds but does not save a Post
post = FactoryGirl.build(:post)
post.new_record? # => true
post..new_record? # => false
To not save the associated object, specify :method => :build in the factory:
factory :post do
# ...
association :author, :factory => :user, :method => :build
end
# Builds a User, and then builds a Post, but does not save either
post = FactoryGirl.build(:post)
post.new_record? # => true
post..new_record? # => true
Inheritance
You can easily create multiple factories for the same class without repeating common attributes by nesting factories:
factory :post do
title 'A title'
factory :approved_post do
approved true
end
end
approved_post = FactoryGirl.create(:approved_post)
approved_post.title # => 'A title'
approved_post.approved # => true
You can also assign the parent explicitly:
factory :post do
title 'A title'
end
factory :approved_post, :parent => :post do
approved true
end
As mentioned above, it's good practice to define a basic factory for each class with only the attributes required to create it. Then, create more specific factories that inherit from this basic parent. Factory definitions are still code, so keep them DRY.
Sequences
Unique values in a specific format (for example, e-mail addresses) can be generated using sequences. Sequences are defined by calling sequence in a definition block, and values in a sequence are generated by calling FactoryGirl.generate:
# Defines a new sequence
FactoryGirl.define do
sequence :email do |n|
"person#{n}@example.com"
end
end
FactoryGirl.generate :email
# => "[email protected]"
FactoryGirl.generate :email
# => "[email protected]"
Sequences can be used as attributes:
factory :user do
email
end
Or in lazy attributes:
factory :invite do
invitee { FactoryGirl.generate(:email) }
end
And it's also possible to define an in-line sequence that is only used in a particular factory:
factory :user do
sequence(:email) {|n| "person#{n}@example.com" }
end
You can also override the initial value:
factory :user do
sequence(:email, 1000) {|n| "person#{n}@example.com" }
end
Without a block, the value will increment itself, starting at its initial value:
factory :post do
sequence(:position)
end
Traits
Traits allow you to group attributes together and then apply them to any factory.
factory :user, :aliases => [:author]
factory :story do
title "My awesome story"
trait :published do
published true
end
trait :unpublished do
published false
end
trait :week_long_publishing do
start_at { 1.week.ago }
end_at { Time.now }
end
trait :month_long_publishing do
start_at { 1.month.ago }
end_at { Time.now }
end
factory :week_long_published_story, :traits => [:published, :week_long_publishing]
factory :month_long_published_story, :traits => [:published, :month_long_publishing]
factory :week_long_unpublished_story, :traits => [:unpublished, :week_long_publishing]
factory :month_long_unpublished_story, :traits => [:unpublished, :month_long_publishing]
end
Traits can be used as attributes:
factory :week_long_published_story_with_title, :parent => :story do
published
week_long_publishing
title { "Publishing that was started at {start_at}" }
end
Traits that define the same attributes won't raise AttributeDefinitionErrors; the trait that defines the attribute latest gets precedence.
factory :user do
name "Friendly User"
login { name }
trait :male do
name "John Doe"
gender "Male"
login { "#{name} (M)" }
end
trait :female do
name "Jane Doe"
gender "Female"
login { "#{name} (F)" }
end
trait :admin do
admin true
login { "admin-#{name}" }
end
factory :male_admin, :traits => [:male, :admin] # login will be "admin-John Doe"
factory :female_admin, :traits => [:admin, :female] # login will be "Jane Doe (F)"
end
You can also override individual attributes granted by a trait in subclasses.
factory :user do
name "Friendly User"
login { name }
trait :male do
name "John Doe"
gender "Male"
login { "#{name} (M)" }
end
factory :brandon do
male
name "Brandon"
end
end
Traits can also be passed in as a list of symbols when you construct an instance from FactoryGirl.
factory :user do
name "Friendly User"
trait :male do
name "John Doe"
gender "Male"
end
trait :admin do
admin true
end
end
# creates an admin user with gender "Male" and name "Jon Snow"
FactoryGirl.create(:user, :admin, :male, :name => "Jon Snow")
This ability works with build, build_stubbed, attributes_for, and create.
Callbacks
factory_girl makes available three callbacks for injecting some code:
- after_build - called after a factory is built (via FactoryGirl.build)
- after_create - called after a factory is saved (via FactoryGirl.create)
- after_stub - called after a factory is stubbed (via FactoryGirl.stub)
Examples:
# Define a factory that calls the generate_hashed_password method after it is built
factory :user do
after_build { |user| generate_hashed_password(user) }
end
Note that you'll have an instance of the user in the block. This can be useful.
You can also define multiple types of callbacks on the same factory:
factory :user do
after_build { |user| do_something_to(user) }
after_create { |user| do_something_else_to(user) }
end
Factories can also define any number of the same kind of callback. These callbacks will be executed in the order they are specified:
factory :user do
after_create { this_runs_first }
after_create { then_this }
end
Calling FactoryGirl.create will invoke both after_build and after_create callbacks.
Also, like standard attributes, child factories will inherit (and can also define) callbacks from their parent factory.
Modifying factories
If you're given a set of factories (say, from a gem developer) but want to change them to fit into your application better, you can modify that factory instead of creating a child factory and adding attributes there.
If a gem were to give you a User factory:
FactoryGirl.define do
factory :user do
full_name "John Doe"
sequence(:username) {|n| "user#{n}" }
password "password"
end
end
Instead of creating a child factory that added additional attributes:
FactoryGirl.define do
factory :application_user, :parent => :user do
full_name { Faker::Name.name }
date_of_birth { 21.years.ago }
gender "Female"
health 90
end
end
You could modify that factory instead.
FactoryGirl.modify do
factory :user do
full_name { Faker::Name.name }
date_of_birth { 21.years.ago }
gender "Female"
health 90
end
end
When modifying a factory, you can change any of the attributes you want (aside from callbacks).
FactoryGirl.modify must be called outside of a FactoryGirl.define block as it operates on factories differently.
A caveat: you can only modify factories (not sequences or traits) and callbacks still compound as they normally would. So, if
the factory you're modifying defines an after_create callback, you defining an after_create won't override it, it'll just get run after the first callback.
Building or Creating Multiple Records
Sometimes, you'll want to create or build multiple instances of a factory at once.
built_users = FactoryGirl.build_list(:user, 25)
created_users = FactoryGirl.create_list(:user, 25)
These methods will build or create a specific amount of factories and return them as an array. To set the attributes for each of the factories, you can pass in a hash as you normally would.
twenty_year_olds = FactoryGirl.build_list(:user, 25, :date_of_birth => 20.years.ago)
Cucumber Integration
factory_girl ships with step definitions that make calling factories from Cucumber easier. To use them, add the following to features/support/env.rb:
require 'factory_girl/step_definitions'
Alternate Syntaxes
Users' tastes for syntax vary dramatically, but most users are looking for a common feature set. Because of this factory_girl supports "syntax layers" which provide alternate interfaces. See Factory::Syntax for information about the various layers available. For example, the Machinist-style syntax is popular:
require 'factory_girl/syntax/blueprint'
require 'factory_girl/syntax/make'
require 'factory_girl/syntax/sham'
Sham.email {|n| "#{n}@example.com" }
User.blueprint do
name { 'Billy Bob' }
email { Sham.email }
end
User.make(:name => 'Johnny')