How to Generate Fake Data for Testing Your Rails App

For a while, I created my own test data, manually, in every single test. It was tedious and took a bit of creative energy because I also tried to make the test data Stars Wars themed 😅. Eventually I came across some data that was a bit too tedious for me to create on my own and I decided that it was time to start generating it. And it was actually incredibly easy to implement, and I’ll never manually create test data again! It makes your code simpler and more concise.

  1. Install the gems you’ll need: factory-bot-rails and faker. Add gem factory-bot-rails and gem 'faker' to your Gemfile under the test and development sections and run bundle install.

  2. Create a “factory” using FactoryBot and Faker. A factory tells FactoryBot how to make test data and Faker actually makes the fake data. You can put factories anywhere in your app, but I put them in spec/factories.rb

     # spec/factories.rb
     FactoryBot.define do
         factory :user do
             username { Faker::Internet.username }
             password { Faker::Internet.password }

Faker has excellent generators to generate test data for addresses, names, numbers, and even more fun stuff like Cosmere generators.

  1. Add a helper method to spec/rails_helper.rb to simplify your tests:

     # spec/rails_helper.rb
     RSpec.configure do |config|
         config.include FactoryBot::Syntax::Methods
  2. Now you can use your factories to make test data in your tests!

     # spec/system/sign_in_spec.rb
     require 'rails_helper'
     RSpec.describe 'Sign in', type: :system do
         scenario 'valid inputs' do
             user = create(:user) # This is the line that uses FactoryBot and Faker!
             visit '/'
             click_link 'Sign In'
             fill_in 'Email', with:
             fill_in 'Password', with: user.password
             click_on 'Sign In!'
             expect(page).to have_content('Signed in successfully.')