How We Made Unit Testing Part of Our Engineering Culture
Article Summary
Instawork runs over 1 million tests daily in their CI pipeline. Here's how they made unit testing a core engineering practice, not an afterthought.
Duncan Edwards from Instawork's engineering team shares their journey building a robust testing culture. They've grown to 30,000+ Python unit tests with strategies that go beyond just measuring coverage.
Key Takeaways
- Sonarcloud decorates every PR with coverage metrics for new and modified code
- Special CI job runs tests at dangerous times: New Year's, daylight savings changeovers
- Factory Boy with LazyAttribute prevents time-freezing issues in test factories
- GitHub Copilot generates initial test implementations from meaningful test names
- Pytest-xdist enables parallel test execution with database isolation per thread
Critical Insight
Instawork combines cultural commitment with automated tooling (coverage tracking, time-based flakiness detection, AI assistance) to maintain high-quality unit tests at scale.
