Lessons learned from a huge Rails app Nahuel Garbezza @ngarbezza

Olá! Hi! Hola!

Who I am!

How big is an application? How can we measure it?

Ways to measure an application size > ActiveRecord::Base.descendants.size => 557 $ git shortlog -s | wc -l 302

Ways to measure an application size > Rails::Engine.subclasses.sum { |e| e.routes.routes.size } => 1554 Bundle complete! 234 Gemfile dependencies, 459 gems now installed.

the context

Context I worked with

“big” means “out of control”

but “out of control” is not bad if you trust your team

Working together as a group! Building trust in your engineering team

what to do with non-Rails code? business logic

/lib $ tree lib/ lib/ ├── additional_params.rb ├── address_validator.rb ├── aol_integration.rb ├── api_throttled_client.rb ├── bad_login_detector.rb ├── cache_keys_invalidator.rb ├── command_interpreter.rb ├── customer_survey.rb ├── default_operation.rb ├── html_errors_formatter.rb ├── json_to_xml_to_json.rb ├── log_middleware.rb ├── measure_converter.rb ├── money_helper.rb ├── one_time_activation.rb ├── product_selector.rb ├── profit_calculator.rb ├── registration_step.rb ├── sharing_policy.rb ├── stuff.rb ├── unknown_identity.rb ├── url_generator.rb ├── user_search_result.rb ├── world_changer.rb ├── xml_utilities.rb └── ...

modularization

what to do with non-Rails code? interfaces entry points Modularization

modularization (level 1) namespaces

what to do with non-Rails code? api/integrations/facebook Api::Integrations::Facebook Modularization using Namespaces

modularization (level 2) Rails engines

what to do with non-Rails code? Modularization using Rails engines

build a test suite you can trust

build a test suite you can trust https://medium.com/@kentbeck_7670/test-desiderata-94150638a4b3

“self-growing” tests

build a test suite you can trust class Conference < ApplicationRecord has_many :attendants end class Attendant < ApplicationRecord belongs_to :conference end “Self-growing” test: check for factories validity FactoryBot.define do factory :conference do title { 'RubyConfBR 2019' } description { 'foo' } end factory :attendant do name { ‘Nahuel’ } conference end end

build a test suite you can trust class FactoriesValidityTest < ActiveSupport::TestCase all_factory_names = FactoryBot.factories.map(&:name) all_factory_names.each do |factory_name| test "factory #{factory_name} creates a valid object" do instance = FactoryBot.build(factory_name) assert_equal true, instance.valid? end end end “Self-growing” test: check for factories validity 1 test running N different instances

build a test suite you can trust class Conference < ApplicationRecord has_many :attendants validates :description, length: { minimum: 20 } end class Attendant < ApplicationRecord belongs_to :conference end “Self-growing” test: check for factories validity FactoryBot.define do factory :conference do title { 'RubyConfBR 2019' } description { 'foo' } end factory :attendant do name { ‘Nahuel’ } conference end end Oops

build a test suite you can trust class FactoriesValidityTest < ActiveSupport::TestCase all_factory_names = FactoryBot.factories.map(&:name) all_factory_names.each do |factory_name| test "factory #{factory_name} creates a valid object" do instance = FactoryBot.build(factory_name) assert_equal true, instance.valid? end end end “Self-growing” test: check for factories validity Feedback about problems in one of our factories

fight against flaky tests ツ

build a test suite you can trust Most common flaky tests causes

test your tests

build a test suite you can trust Mutation Testing expecting the tests to fail https://github.com/mbj/mutant Testing our tests with Mutation Testing

taking care of your production errors

track notified alerts protocol fix and improve Taking care of production errors

Errors give you great feedback Taking care of production errors

bonus

No content

Muito obrigado! Thank you so much! Muchas gracias!

Creative Software Development