Jay Tennier: How Testing Platform Rainforest QA Tests Itself

On Rails

In this episode of On Rails, Robby is joined by Jay Tennier, Engineering Manager at Rainforest QA, where he's spent over seven years working across a long-lived Rails monolith and supporting services. They explore how Rainforest maintains their platform with a small team, and the practical decisions that come with that reality. Jay shares lessons from pulling microservices back into the monolith, why they wrap third-party services in adapters, and how they push analytics work to BigQuery instead of straining their Rails database. The conversation covers testing philosophy including "wet tests" over DRY abstractions, using dry-monads for complex service flows, and how celebrating code deletion has become part of their engineering culture.

Social + Web Presence

LinkedIn: https://www.linkedin.com/in/jaytennier/
GitHub: https://github.com/jaytennie/

Twitter/X: https://x.com/jaytennier
Bluesky: https://bsky.app/profile/jaytennier.bsky.social

Company/Org Links

Homepage: https://www.rainforestqa.com/

Tools & Libraries Mentioned
Active Record: Rails ORM.

BigQuery: Hosted analytics warehouse.

Cube.js: API layer for querying analytics data.

DRY-Monads: Structured success/failure flow.

FactoryBot: Test data factories.

Grape: Ruby API framework.

GoodJob: Background job processor.

Q Classic: DB-backed job queue.

Redash: SQL-based dashboards and reporting.

RSpec: Rails testing framework.

React: Front-end application framework.

Haml: Legacy templating engine.

Segment / Mixpanel: Event tracking pipelines.

Books Mentioned

Confident Ruby by Avdi Grimm

Exceptional Ruby by Avdi Grimm

Working Effectively with Legacy Code by Michael Feathers

Send us a text

On Rails is a podcast focused on real-world technical decision-making, exploring how teams are scaling, architecting, and solving complex challenges with Rails.

On Rails is brought to you by The Rails Foundation, and hosted by Robby Russell of Planet Argon, a consultancy that helps teams modernize their Ruby on Rails applications.

Capitoli

1. Intro and welcome to Jay from Rainforest QA (00:00:00)

2. What keeps Jay "On Rails" since version 0.13 (00:01:12)

3. Overview of Rainforest QA's platform and architecture (00:04:52)

4. React frontend in separate repo and API strategy (00:14:40)

5. Team size evolution: from 40+ engineers down to 7 (00:22:28)

6. Failed experiments and the dry-monads pattern (00:25:35)

7. Data retention policies and deprovisioning clients (00:32:25)

8. Lessons from pulling microservices back into the monolith (00:36:01)

9. Building adapter layers for third-party services (00:41:39)

10. Testing philosophy: preferring "wet tests" over DRY (00:57:42)

11. Pushing analytics to BigQuery instead of Rails (01:08:54)

12. When to sunset services and delete code (01:17:31)

13. Transitioning into management and supporting the team (01:24:01)

14. Is Rails part of Rainforest's secret sauce? (01:32:47)

15. Book recommendations and where to follow Jay's work (01:37:14)