Getting Started =============== Update Your Gemfile ------------------- If you're using Rails: ```ruby gem "factory_bot_rails" ``` If you're *not* using Rails: ```ruby gem "factory_bot" ``` JRuby users: factory_bot works with JRuby starting with 1.6.7.2 (latest stable, as per July 2012). JRuby has to be used in 1.9 mode, for that, use JRUBY_OPTS environment variable: ```bash export JRUBY_OPTS=--1.9 ``` Once your Gemfile is updated, you'll want to update your bundle. Configure your test suite ------------------------- ### RSpec If you're using Rails: ```ruby RSpec.configure do |config| config.include FactoryBot::Syntax::Methods end ``` If you're *not* using Rails: ```ruby RSpec.configure do |config| config.include FactoryBot::Syntax::Methods config.before(:suite) do FactoryBot.find_definitions end end ``` ### Test::Unit ```ruby class Test::Unit::TestCase include FactoryBot::Syntax::Methods end ``` ### Cucumber ```ruby # env.rb (Rails example location - RAILS_ROOT/features/support/env.rb) World(FactoryBot::Syntax::Methods) ``` ### Spinach ```ruby class Spinach::FeatureSteps include FactoryBot::Syntax::Methods end ``` ### Minitest ```ruby class Minitest::Unit::TestCase include FactoryBot::Syntax::Methods end ``` ### Minitest::Spec ```ruby class Minitest::Spec include FactoryBot::Syntax::Methods end ``` ### minitest-rails ```ruby class ActiveSupport::TestCase include FactoryBot::Syntax::Methods end ``` If you do not include `FactoryBot::Syntax::Methods` in your test suite, then all factory_bot methods will need to be prefaced with `FactoryBot`. 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: ```ruby # This will guess the User class FactoryBot.define do factory :user do first_name { "John" } last_name { "Doe" } admin { false } end end ``` It is also possible to explicitly specify the class: ```ruby # This will use the User class (otherwise Admin would have been guessed) factory :admin, class: User ``` If the constant is not available (if you are using a Rails engine that waits to load models, for example), you can also pass a symbol or string, which factory_bot will constantize later, once you start building objects: ```ruby # It's OK if Doorkeeper::AccessToken isn't loaded yet factory :access_token, class: "Doorkeeper::AccessToken" ``` Because of the block syntax in Ruby, defining attributes as `Hash`es (for serialized/JSON columns, for example) requires two sets of curly brackets: ```ruby factory :program do configuration { { auto_resolve: false, auto_define: true } } 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 after calling `FactoryBot.find_definitions` if factories are defined in files at the following locations: test/factories.rb spec/factories.rb test/factories/*.rb spec/factories/*.rb Using factories --------------- factory\_bot supports several different build strategies: build, create, attributes\_for and build\_stubbed: ```ruby # Returns a User instance that's not saved user = build(:user) # Returns a saved User instance user = create(:user) # Returns a hash of attributes that can be used to build a User instance attrs = attributes_for(:user) # Returns an object with all defined attributes stubbed out stub = build_stubbed(:user) # Passing a block to any of the methods above will yield the return object 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: ```ruby # Build a User instance and override the first_name property user = build(:user, first_name: "Joe") user.first_name # => "Joe" ``` Note that objects created with `build_stubbed` cannot be serialized with `Marshal.dump`, since factory_bot defines singleton methods on these objects. Static Attributes ------------------ Static attributes (without a block) are no longer available in factory\_bot 5. You can read more about the decision to remove them in [this blog post](https://robots.thoughtbot.com/deprecating-static-attributes-in-factory_bot-4-11). Aliases ------- factory_bot allows you to define aliases to existing factories to make them easier to re-use. This could come in handy when, for example, your Post object has an author attribute that actually refers to an instance of a User class. While normally factory_bot can infer the factory name from the association name, in this case it will look for an author factory in vain. So, alias your user factory so it can be used under alias names. ```ruby factory :user, aliases: [:author, :commenter] do first_name { "John" } last_name { "Doe" } date_of_birth { 18.years.ago } end factory :post do author # 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 evaluator that is yielded to dynamic attribute blocks: ```ruby factory :user do first_name { "Joe" } last_name { "Blow" } email { "#{first_name}.#{last_name}@example.com".downcase } end create(:user, last_name: "Doe").email # => "joe.doe@example.com" ``` Transient Attributes -------------------- There may be times where your code can be DRYed up by passing in transient attributes to factories. ```ruby factory :user do transient do rockstar { true } upcased { false } end name { "John Doe#{" - Rockstar" if rockstar}" } email { "#{name.downcase}@example.com" } after(:create) do |user, evaluator| user.name.upcase! if evaluator.upcased end end create(:user, upcased: true).name #=> "JOHN DOE - ROCKSTAR" ``` Transient 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_bot's dynamic attributes, you can access transient attributes as you would expect. If you need to access the evaluator in a factory_bot callback, you'll need to declare a second block argument (for the evaluator) and access transient attributes from there. Method Name / Reserved Word Attributes ------------------------------- If your attributes conflict with existing methods or reserved words (all methods in the [DefinitionProxy](https://github.com/thoughtbot/factory_bot/blob/master/lib/factory_bot/definition_proxy.rb) class) you can define them with `add_attribute`. ```ruby factory :dna do add_attribute(:sequence) { 'GATTACA' } end factory :payment do add_attribute(:method) { 'paypal' } end ``` Inheritance ----------- You can easily create multiple factories for the same class without repeating common attributes by nesting factories: ```ruby factory :post do title { "A title" } factory :approved_post do approved { true } end end approved_post = create(:approved_post) approved_post.title # => "A title" approved_post.approved # => true ``` You can also assign the parent explicitly: ```ruby 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. 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. ```ruby factory :post do # ... author end ``` You can also specify a different factory or override attributes: ```ruby factory :post do # ... association :author, factory: :user, last_name: "Writely" end ``` In factory\_bot 5, associations default to using the same build strategy as their parent object: ```ruby FactoryBot.define do factory :author factory :post do author end end post = build(:post) post.new_record? # => true post.author.new_record? # => true post = create(:post) post.new_record? # => false post.author.new_record? # => false ``` This is different than the default behavior for previous versions of factory\_bot, where the association strategy would not always match the strategy of the parent object. If you want to continue using the old behavior, you can set the `use_parent_strategy` configuration option to `false`. ```ruby FactoryBot.use_parent_strategy = false # Builds and saves a User and a Post post = create(:post) post.new_record? # => false post.author.new_record? # => false # Builds and saves a User, and then builds but does not save a Post post = build(:post) post.new_record? # => true post.author.new_record? # => false ``` To not save the associated object, specify strategy: :build in the factory: ```ruby FactoryBot.use_parent_strategy = false factory :post do # ... association :author, factory: :user, strategy: :build end # Builds a User, and then builds a Post, but does not save either post = build(:post) post.new_record? # => true post.author.new_record? # => true ``` Please note that the `strategy: :build` option must be passed to an explicit call to `association`, and cannot be used with implicit associations: ```ruby factory :post do # ... author strategy: :build # <<< this does *not* work; causes author_id to be nil ``` Generating data for a `has_many` relationship is a bit more involved, depending on the amount of flexibility desired, but here's a surefire example of generating associated data. ```ruby FactoryBot.define do # post factory with a `belongs_to` association for the user factory :post do title { "Through the Looking Glass" } user end # user factory without associated posts factory :user do name { "John Doe" } # user_with_posts will create post data after the user has been created factory :user_with_posts do # posts_count is declared as a transient attribute and available in # attributes on the factory, as well as the callback via the evaluator transient do posts_count { 5 } end # the after(:create) yields two values; the user instance itself and the # evaluator, which stores all values from the factory, including transient # attributes; `create_list`'s second argument is the number of records # to create and we make sure the user is associated properly to the post after(:create) do |user, evaluator| create_list(:post, evaluator.posts_count, user: user) end end end end ``` This allows us to do: ```ruby create(:user).posts.length # 0 create(:user_with_posts).posts.length # 5 create(:user_with_posts, posts_count: 15).posts.length # 15 ``` Generating data for a `has_and_belongs_to_many` relationship is very similar to the above `has_many` relationship, with a small change, you need to pass an array of objects to the model's pluralized attribute name rather than a single object to the singular version of the attribute name. Here's an example with two models that are related via `has_and_belongs_to_many`: ```ruby FactoryBot.define do # language factory with a `belongs_to` association for the profile factory :language do title { "Through the Looking Glass" } profile end # profile factory without associated languages factory :profile do name { "John Doe" } # profile_with_languages will create language data after the profile has # been created factory :profile_with_languages do # languages_count is declared as an ignored attribute and available in # attributes on the factory, as well as the callback via the evaluator transient do languages_count { 5 } end # the after(:create) yields two values; the profile instance itself and # the evaluator, which stores all values from the factory, including # ignored attributes; `create_list`'s second argument is the number of # records to create and we make sure the profile is associated properly # to the language after(:create) do |profile, evaluator| create_list(:language, evaluator.languages_count, profiles: [profile]) end end end end ``` This allows us to do: ```ruby create(:profile).languages.length # 0 create(:profile_with_languages).languages.length # 5 create(:profile_with_languages, languages_count: 15).languages.length # 15 ``` 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) ``` 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 `generate`: ```ruby # Defines a new sequence FactoryBot.define do sequence :email do |n| "person#{n}@example.com" end end generate :email # => "person1@example.com" generate :email # => "person2@example.com" ``` Sequences can be used in dynamic attributes: ```ruby factory :invite do invitee { generate(:email) } end ``` Or as implicit attributes: ```ruby factory :user do email # Same as `email { generate(:email) }` end ``` Note that defining sequences as implicit attributes will not work if you have a factory with the same name as the sequence. And it's also possible to define an in-line sequence that is only used in a particular factory: ```ruby factory :user do sequence(:email) { |n| "person#{n}@example.com" } end ``` You can also override the initial value: ```ruby 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: ```ruby factory :post do sequence(:position) end ``` Sequences can also have aliases. The sequence aliases share the same counter: ```ruby factory :user do sequence(:email, 1000, aliases: [:sender, :receiver]) { |n| "person#{n}@example.com" } end # will increase value counter for :email which is shared by :sender and :receiver generate(:sender) ``` Define aliases and use default value (1) for the counter ```ruby factory :user do sequence(:email, aliases: [:sender, :receiver]) { |n| "person#{n}@example.com" } end ``` Setting the value: ```ruby factory :user do sequence(:email, 'a', aliases: [:sender, :receiver]) { |n| "person#{n}@example.com" } end ``` The value just needs to support the `#next` method. Here the next value will be 'a', then 'b', etc. Sequences can also be rewound with `FactoryBot.rewind_sequences`: ```ruby sequence(:email) {|n| "person#{n}@example.com" } generate(:email) # "person1@example.com" generate(:email) # "person2@example.com" generate(:email) # "person3@example.com" FactoryBot.rewind_sequences generate(:email) # "person1@example.com" ``` This rewinds all registered sequences. Traits ------ Traits allow you to group attributes together and then apply them to any factory. ```ruby factory :user, aliases: [:author] factory :story do title { "My awesome story" } author 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 implicit attributes: ```ruby factory :week_long_published_story_with_title, parent: :story do published week_long_publishing title { "Publishing that was started at #{start_at}" } end ``` Note that defining traits as implicit attributes will not work if you have a factory or sequence with the same name as the trait. Traits that define the same attributes won't raise AttributeDefinitionErrors; the trait that defines the attribute latest gets precedence. ```ruby 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. ```ruby 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 factory_bot. ```ruby 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" create(:user, :admin, :male, name: "Jon Snow") ``` This ability works with `build`, `build_stubbed`, `attributes_for`, and `create`. `create_list` and `build_list` methods are supported as well. Just remember to pass the number of instances to create/build as second parameter, as documented in the "Building or Creating Multiple Records" section of this file. ```ruby factory :user do name { "Friendly User" } trait :admin do admin { true } end end # creates 3 admin users with gender "Male" and name "Jon Snow" create_list(:user, 3, :admin, :male, name: "Jon Snow") ``` Traits can be used with associations easily too: ```ruby factory :user do name { "Friendly User" } trait :admin do admin { true } end end factory :post do association :user, :admin, name: 'John Doe' end # creates an admin user with name "John Doe" create(:post).user ``` When you're using association names that're different than the factory: ```ruby factory :user do name { "Friendly User" } trait :admin do admin { true } end end factory :post do association :author, :admin, factory: :user, name: 'John Doe' # or association :author, factory: [:user, :admin], name: 'John Doe' end # creates an admin user with name "John Doe" create(:post).author ``` Traits can be used within other traits to mix in their attributes. ```ruby factory :order do trait :completed do completed_at { 3.days.ago } end trait :refunded do completed refunded_at { 1.day.ago } end end ``` Finally, traits can accept transient attributes. ```ruby factory :invoice do trait :with_amount do transient do amount { 1 } end after(:create) do |invoice, evaluator| create :line_item, invoice: invoice, amount: evaluator.amount end end end create :invoice, :with_amount, amount: 2 ``` Callbacks --------- factory\_bot makes available four callbacks for injecting some code: * after(:build) - called after a factory is built (via `FactoryBot.build`, `FactoryBot.create`) * before(:create) - called before a factory is saved (via `FactoryBot.create`) * after(:create) - called after a factory is saved (via `FactoryBot.create`) * after(:stub) - called after a factory is stubbed (via `FactoryBot.build_stubbed`) Examples: ```ruby # 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: ```ruby 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: ```ruby factory :user do after(:create) { this_runs_first } after(:create) { then_this } end ``` Calling `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. Multiple callbacks can be assigned to run a block; this is useful when building various strategies that run the same code (since there are no callbacks that are shared across all strategies). ```ruby factory :user do callback(:after_stub, :before_create) { do_something } after(:stub, :create) { do_something_else } before(:create, :custom) { do_a_third_thing } end ``` To override callbacks for all factories, define them within the `FactoryBot.define` block: ```ruby FactoryBot.define do after(:build) { |object| puts "Built #{object}" } after(:create) { |object| AuditLog.create(attrs: object.attributes) } factory :user do name { "John Doe" } end end ``` You can also call callbacks that rely on `Symbol#to_proc`: ```ruby # app/models/user.rb class User < ActiveRecord::Base def confirm! # confirm the user account end end # spec/factories.rb FactoryBot.define do factory :user do after :create, &:confirm! end end create(:user) # creates the user and confirms it ``` 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: ```ruby FactoryBot.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: ```ruby FactoryBot.define do factory :application_user, parent: :user do full_name { "Jane Doe" } date_of_birth { 21.years.ago } gender { "Female" } health { 90 } end end ``` You could modify that factory instead. ```ruby FactoryBot.modify do factory :user do full_name { "Jane Doe" } 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). `FactoryBot.modify` must be called outside of a `FactoryBot.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. ```ruby built_users = build_list(:user, 25) created_users = 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. ```ruby twenty_year_olds = build_list(:user, 25, date_of_birth: 20.years.ago) ``` `build_stubbed_list` will give you fully stubbed out instances: ```ruby stubbed_users = build_stubbed_list(:user, 25) # array of stubbed users ``` There's also a set of `*_pair` methods for creating two records at a time: ```ruby built_users = build_pair(:user) # array of two built users created_users = create_pair(:user) # array of two created users ``` If you need multiple attribute hashes, `attributes_for_list` will generate them: ```ruby users_attrs = attributes_for_list(:user, 25) # array of attribute hashes ``` Linting Factories ----------------- factory_bot allows for linting known factories: ```ruby FactoryBot.lint ``` `FactoryBot.lint` creates each factory and catches any exceptions raised during the creation process. `FactoryBot::InvalidFactoryError` is raised with a list of factories (and corresponding exceptions) for factories which could not be created. Recommended usage of `FactoryBot.lint` is to run this in a task before your test suite is executed. Running it in a `before(:suite)`, will negatively impact the performance of your tests when running single tests. Example Rake task: ```ruby # lib/tasks/factory_bot.rake namespace :factory_bot do desc "Verify that all FactoryBot factories are valid" task lint: :environment do if Rails.env.test? DatabaseCleaner.clean_with(:deletion) DatabaseCleaner.cleaning do FactoryBot.lint end else system("bundle exec rake factory_bot:lint RAILS_ENV='test'") fail if $?.exitstatus.nonzero? end end end ``` After calling `FactoryBot.lint`, you'll likely want to clear out the database, as records will most likely be created. The provided example above uses the database_cleaner gem to clear out the database; be sure to add the gem to your Gemfile under the appropriate groups. You can lint factories selectively by passing only factories you want linted: ```ruby factories_to_lint = FactoryBot.factories.reject do |factory| factory.name =~ /^old_/ end FactoryBot.lint factories_to_lint ``` This would lint all factories that aren't prefixed with `old_`. Traits can also be linted. This option verifies that each and every trait of a factory generates a valid object on its own. This is turned on by passing `traits: true` to the `lint` method: ```ruby FactoryBot.lint traits: true ``` This can also be combined with other arguments: ```ruby FactoryBot.lint factories_to_lint, traits: true ``` You can also specify the strategy used for linting: ```ruby FactoryBot.lint strategy: :build ``` Verbose linting will include full backtraces for each error, which can be helpful for debugging: ```ruby FactoryBot.lint verbose: true ``` Custom Construction ------------------- If you want to use factory_bot to construct an object where some attributes are passed to `initialize` or if you want to do something other than simply calling `new` on your build class, you can override the default behavior by defining `initialize_with` on your factory. Example: ```ruby # user.rb class User attr_accessor :name, :email def initialize(name) @name = name end end # factories.rb sequence(:email) { |n| "person#{n}@example.com" } factory :user do name { "Jane Doe" } email initialize_with { new(name) } end build(:user).name # Jane Doe ``` Although factory_bot is written to work with ActiveRecord out of the box, it can also work with any Ruby class. For maximum compatibility with ActiveRecord, the default initializer builds all instances by calling `new` on your build class without any arguments. It then calls attribute writer methods to assign all the attribute values. While that works fine for ActiveRecord, it actually doesn't work for almost any other Ruby class. You can override the initializer in order to: * Build non-ActiveRecord objects that require arguments to `initialize` * Use a method other than `new` to instantiate the instance * Do crazy things like decorate the instance after it's built When using `initialize_with`, you don't have to declare the class itself when calling `new`; however, any other class methods you want to call will have to be called on the class explicitly. For example: ```ruby factory :user do name { "John Doe" } initialize_with { User.build_with_name(name) } end ``` You can also access all public attributes within the `initialize_with` block by calling `attributes`: ```ruby factory :user do transient do comments_count { 5 } end name "John Doe" initialize_with { new(attributes) } end ``` This will build a hash of all attributes to be passed to `new`. It won't include transient attributes, but everything else defined in the factory will be passed (associations, evaluated sequences, etc.) You can define `initialize_with` for all factories by including it in the `FactoryBot.define` block: ```ruby FactoryBot.define do initialize_with { new("Awesome first argument") } end ``` When using `initialize_with`, attributes accessed from within the `initialize_with` block are assigned *only* in the constructor; this equates to roughly the following code: ```ruby FactoryBot.define do factory :user do initialize_with { new(name) } name { 'value' } end end build(:user) # runs User.new('value') ``` This prevents duplicate assignment; in versions of factory_bot before 4.0, it would run this: ```ruby FactoryBot.define do factory :user do initialize_with { new(name) } name { 'value' } end end build(:user) # runs user = User.new('value') user.name = 'value' ``` Custom Strategies ----------------- There are times where you may want to extend behavior of factory\_bot by adding a custom build strategy. Strategies define two methods: `association` and `result`. `association` receives a `FactoryBot::FactoryRunner` instance, upon which you can call `run`, overriding the strategy if you want. The second method, `result`, receives a `FactoryBot::Evaluation` instance. It provides a way to trigger callbacks (with `notify`), `object` or `hash` (to get the result instance or a hash based on the attributes defined in the factory), and `create`, which executes the `to_create` callback defined on the factory. To understand how factory\_bot uses strategies internally, it's probably easiest to just view the source for each of the four default strategies. Here's an example of composing a strategy using `FactoryBot::Strategy::Create` to build a JSON representation of your model. ```ruby class JsonStrategy def initialize @strategy = FactoryBot.strategy_by_name(:create).new end delegate :association, to: :@strategy def result(evaluation) @strategy.result(evaluation).to_json end end ``` For factory\_bot to recognize the new strategy, you can register it: ```ruby FactoryBot.register_strategy(:json, JsonStrategy) ``` This allows you to call ```ruby FactoryBot.json(:user) ``` Finally, you can override factory\_bot's own strategies if you'd like by registering a new object in place of the strategies. Custom Callbacks ---------------- Custom callbacks can be defined if you're using custom strategies: ```ruby class JsonStrategy def initialize @strategy = FactoryBot.strategy_by_name(:create).new end delegate :association, to: :@strategy def result(evaluation) result = @strategy.result(evaluation) evaluation.notify(:before_json, result) result.to_json.tap do |json| evaluation.notify(:after_json, json) evaluation.notify(:make_json_awesome, json) end end end FactoryBot.register_strategy(:json, JsonStrategy) FactoryBot.define do factory :user do before(:json) { |user| do_something_to(user) } after(:json) { |user_json| do_something_to(user_json) } callback(:make_json_awesome) { |user_json| do_something_to(user_json) } end end ``` Custom Methods to Persist Objects --------------------------------- By default, creating a record will call `save!` on the instance; since this may not always be ideal, you can override that behavior by defining `to_create` on the factory: ```ruby factory :different_orm_model do to_create { |instance| instance.persist! } end ``` To disable the persistence method altogether on create, you can `skip_create` for that factory: ```ruby factory :user_without_database do skip_create end ``` To override `to_create` for all factories, define it within the `FactoryBot.define` block: ```ruby FactoryBot.define do to_create { |instance| instance.persist! } factory :user do name { "John Doe" } end end ``` ActiveSupport Instrumentation ----------------------------- In order to track what factories are created (and with what build strategy), `ActiveSupport::Notifications` are included to provide a way to subscribe to factories being run. One example would be to track factories based on a threshold of execution time. ```ruby ActiveSupport::Notifications.subscribe("factory_bot.run_factory") do |name, start, finish, id, payload| execution_time_in_seconds = finish - start if execution_time_in_seconds >= 0.5 $stderr.puts "Slow factory: #{payload[:name]} using strategy #{payload[:strategy]}" end end ``` Another example would be tracking all factories and how they're used throughout your test suite. If you're using RSpec, it's as simple as adding a `before(:suite)` and `after(:suite)`: ```ruby factory_bot_results = {} config.before(:suite) do ActiveSupport::Notifications.subscribe("factory_bot.run_factory") do |name, start, finish, id, payload| factory_name = payload[:name] strategy_name = payload[:strategy] factory_bot_results[factory_name] ||= {} factory_bot_results[factory_name][strategy_name] ||= 0 factory_bot_results[factory_name][strategy_name] += 1 end end config.after(:suite) do puts factory_bot_results end ``` Rails Preloaders and RSpec -------------------------- When running RSpec with a Rails preloader such as `spring` or `zeus`, it's possible to encounter an `ActiveRecord::AssociationTypeMismatch` error when creating a factory with associations, as below: ```ruby FactoryBot.define do factory :united_states, class: Location do name { 'United States' } association :location_group, factory: :north_america end factory :north_america, class: LocationGroup do name { 'North America' } end end ``` The error occurs during the run of the test suite: ``` Failure/Error: united_states = create(:united_states) ActiveRecord::AssociationTypeMismatch: LocationGroup(#70251250797320) expected, got LocationGroup(#70251200725840) ``` The two possible solutions are to either run the suite without the preloader, or to add `FactoryBot.reload` to the RSpec configuration, like so: ```ruby RSpec.configure do |config| config.before(:suite) { FactoryBot.reload } end ``` Using Without Bundler --------------------- If you're not using Bundler, be sure to have the gem installed and call: ```ruby require 'factory_bot' ``` Once required, assuming you have a directory structure of `spec/factories` or `test/factories`, all you'll need to do is run: ```ruby FactoryBot.find_definitions ``` If you're using a separate directory structure for your factories, you can change the definition file paths before trying to find definitions: ```ruby FactoryBot.definition_file_paths = %w(custom_factories_directory) FactoryBot.find_definitions ``` If you don't have a separate directory of factories and would like to define them inline, that's possible as well: ```ruby require 'factory_bot' FactoryBot.define do factory :user do name { 'John Doe' } date_of_birth { 21.years.ago } end end ```