Andrew Havens Ruby Developer

How to create a new Rails engine which uses RSpec and FactoryGirl for testing

15 April 2013

Need to create a Rails engine which uses RSpec instead of Test::Unit and FactoryGirl instead of fixtures? Here are the steps:

1. Create the engine:

rails plugin new gem_name -T --mountable --full --dummy-path=spec/test_app
  • -T tells the generator to skip Test::Unit
  • --mountable tells the generator that you want a namespaced engine
  • --full tells the generator that you want app and config directories
  • --dummy-path is the rails app that is generated for your tests. It's called test/dummy by default, but I never liked calling it that.

2. Add rails-rspec and factory_girl_rails as a dependencies in your Gemfile:

source ""
gem "rspec-rails", "~> 2.12.2"
gem "factory_girl_rails", "~> 4.0"

Then bundle install.

3. Now edit your engine's lib/gem_name/engine.rb file to include rspec:

module GemName
  class Engine < ::Rails::Engine
    isolate_namespace GemName

    config.generators do |g|
      g.test_framework :rspec
      g.fixture_replacement :factory_girl, :dir => 'spec/factories'

4. Run the rspec generator:

rails generate rspec:install

5. After creating some models and migrations, run the migrations for the test app and the test database:

bundle exec rake app:db:migrate
bundle exec rake app:db:test:prepare

Now you have a Rails engine configured to use RSpec. You're ready to start testing!