Rails Engine with RSpec and Trailblazer

a_setup.md

This example is called "stock". Use your own name instead.

1. Setup new project: rails plugin new stock --mountable -T --dummy-path=spec/dummy
2. Edit gemspec
3. Edit engine.rb
4. Install RSpec: bundle install rails generate rspec:install
5. Make edits to spec/rails_helper.rb according to: http://blog.honeybadger.io/rails4-engine-controller-specs/
6. Create your engine. See example model, concept and test
7. Create migrations and run rake db:migrate
8. Run rspec for tests or spec/dummy/bin/rails s for running test app

engine.rb

# lib/stock/engine.rb

require 'trailblazer'
require 'trailblazer/operation/model'

module Stock
  class Engine < ::Rails::Engine
    isolate_namespace Stock
    
    def self.activate
      Dir.glob(File.join(File.dirname(__FILE__), '../../app/concepts/**/*.rb')) do |c|
        Rails.configuration.cache_classes ? require(c) : load(c)
      end
    end

    config.to_prepare &method(:activate).to_proc
    
    config.generators do |g|
      g.test_framework :rspec
    end
  end
end

location.rb

# app/models/stock/location.rb

module Stock
  class Location < ActiveRecord::Base
  end
end

location_spec.rb

# spec/models/stock/location_spec.rb

require 'rails_helper'

module Stock
  RSpec.describe Location, type: :model do
    it 'persists directly' do
      location = Location.create!(name:'loc1')
      expect(location.persisted?).to be_truthy
      expect(location.name).to eq 'loc1'
    end
    
    it 'persists' do
      location = Stock::Location::Create.(location: {name: 'loc1'}).model

      expect(location.persisted?).to be_truthy
      expect(location.name).to eq 'loc1'
    end
  end
end

operation.rb

# app/concepts/stock/location/operation.rb

module Stock
  class Location < ActiveRecord::Base
    class Create < Trailblazer::Operation
      include Model
      model Location, :create

      contract do
        property :name

        validates :name, presence: true
      end

      def process(params)
        validate(params[:location]) do |f|
          f.save
        end
      end
    end
  end
end

stock.gemspec

$:.push File.expand_path("../lib", __FILE__)

# Maintain your gem's version:
require "stock/version"

# Describe your gem and declare its dependencies:
Gem::Specification.new do |s|
  s.name        = "stock"
  s.version     = Stock::VERSION
  s.authors     = ["TODO"]
  s.email       = ["TODO"]
  s.homepage    = "TODO"
  s.summary     = "TODO"
  s.description = "TODO"
  s.license     = "MIT"

  s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]

  s.add_dependency "rails"
  s.add_development_dependency  'trailblazer'
  s.add_development_dependency  'trailblazer-rails'
  s.add_development_dependency "sqlite3"
  s.add_development_dependency "rspec-rails"
end

It looks as if the pivotal element is the Engine::activate method. If we provide that behaviour in trailblazer-rails and use trailblazer-loader instead of your manual requires, it should all be good.

Not sure if that is enough, since Rails Engines don't automatically require the libraries if they are only specified in the gemspec. They are only required if they are present in the Engines gemfile. And if I put gem trailblazer-rails in the gemfile I get strange path errors.