Factory Bot (Rails Testing)

Factory Bot, originally known as Factory Girl, is a software library for the Ruby programming language that provides factory methods to create test fixtures for automated software testing. The fixture objects can be created on the fly; they may be plain Ruby objects with a predefined state, ORM objects with existing database records or mock objects.

Factory Bot is often used in testing Ruby on Rails applications; where it replaces Rails' built-in fixture mechanism. Rails' default setup uses a pre-populated database as test fixtures, which are global for the complete test suite. Factory Bot, on the other hand, allows developers to define a different setup for each test and thus helps to avoid dependencies within the test suite.

Factories

Defining Factories A factory is defined by a name and its set of attributes. The class of the test object is either determined through the name of the factory or set explicitly.

FactoryBot.define do # Determine class automatically factory :user do name { "Captain Minion" } superhero { false } end

# Specify class explicitly factory :superhero, class: User do name { "Tony Stark" } superhero { true } end end

Features

Traits Traits allow grouping of attributes which can be applied to any factory.

factory :status do title { "Seeking for Full Time jobs" }

trait :international do international { true } end

trait :resident do international { false } end

trait :comp_sci do comp_sci { true } end

trait :electrical do comp_sci { false } end

factory :comp_sci_international_student, traits: [:international, :comp_sci] factory :electrical_resident_student, traits: [:resident, :electrical] end

Alias Factory Bot allows creating aliases for existing factories so that the factories can be reused.

factory :user, aliases: [:student, :teacher] do first_name { "John" } end

factory :notice do teacher # Alias used ''teacher'' for ''user'' title { "Office Hours" } end

factory :notification do student #Alias used student for user title { "Lecture timings" } end

Sequences Factory Bot allows creating unique values for a test attribute in a given format.

FactoryBot.define do factory :title do sequence(:name) {|n| "Title #{n}" } # Title 1, Title 2 and so on... end end

Inheritance Factories can be inherited while creating a factory for a class. This allows the user to reuse common attributes from parent factories and avoid writing duplicate code for duplicate attributes. Factories can be written in a nested fashion to leverage inheritance.

factory :user do name { "Micheal" }

factory :admin do admin_rights true end end

admin_user = create(:admin) admin_user.name # Micheal admin_user.admin_rights # true

Parent factories can also be specified explicitly. factory :user do name { "Micheal" } end

factory :admin, parent: :user do admin_user { true } end

Callback Factory Bot allows custom code to be injected at four different stages: Code can be injected after the factory is built Code can be injected before the factory is saved Code can be injected after the factory is saved Code can be injected before the factory is stubbed

Factory Bot (Rails Testing)

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