Rails Testing: Tips for lightning fast test suites

Have you been taking a lot more coffee breaks lately while you wait for your tests to run? Is it so bad you don’t feel like writing specs for your app anymore? In this talk, I share a few strategies we used to reduce our build time by almost 75% on one of our Ruby on Rails application.

Transcript

1. Rails Testing Tips for lightning⚡ fast test suites Raoul Diffouo Software Engineer Prodigy Finance @diraulo
3. Why do we Test? • Confidence • Legacy systems
6. https://github.com/grosser/parallel_tests
7. Outline • RSpec configurations • Interacting with the Database • Miscellaneous • Wrap-up
8. RSpec configs
9. before spec_helper.rb
10. Split config files • spec_helper.rb contains bare minimum config to run test suites. Keep this file as slim as possible and only add config required by all type of specs • rails_helper.rb contains rails specific config. This will be used for specs that require rails to be loaded. This includes controller, features, system & models specs.
12. Interacting With the Database
13. DB Cleaning Strategies • transaction • truncation • deletion
14. What’s a Transaction? “A transaction, in the context of a database, is a logical unit that is independently executed for data retrieval or updates. In relational databases, database transactions must be atomic, consistent, isolated and durable -- summarized as the ACID acronym.” https://www.techopedia.com/definition/16455/transaction
15. Cleaning with Transaction
16. Cleaning DB with Transaction (cont.) • advantage It’s faster • gotchas - Whatever you create before your tests will remain in the DB - Watch out for specs that are dependent on table IDs. The count won’t reset in between specs - Issues when the test involves multiple DB connections
17. Cleaning DB with truncation
18. Cleaning DB with truncation (cont.) • pro(s) - Completely wipes out your DB in between specs - Helps when you have tests that depend on multiple DB connections • con(s) - It’s very slow
19. Flaky Specs
20. Cleaning DB with transaction
21. You might not need DatabaseCleaner • Rails Transactional Fixtures (Tests) - Have nothing to do with Fixtures - Behave like the transaction strategy of DatabaseCleaner config.use_transactional_fixtures = true • Rails 5.1+ now has better support for multiple DB connections
22. You might not need DatabaseCleaner
25. Miscellaneous
26. Don’t create data using DB Migrations
27. Only create data You need
28. factories: You’re probably using them wrong ☹ • create(:course) returns a model instance and saves it to the DB • build(:course) returns a model instance that has not been saved to the DB • build_stubbed(:course) Like build, returns an unsaved model object. Unlike build, it assigns a fake ActiveRecord ID to the model and stubs out db-interaction methods (like save) Source: Rails 5 Testing Prescriptions
29. Wrap-up
32. Wrap-up • Prefer Transactions over Truncation • Avoid excessive calls to the DB • Only create data you need • Don’t use DB Migrations to seed DBs
33. Resources
34. • http://betterspecs.org • Rails 5 Test Prescriptions • Effective Testing with RSpec 3 • https://github.com/Datab aseCleaner/database_clea ner • https://anti-pattern.com /transactional-fixtures- in-rails
35. Happy Testing