Testing Strategies

A comprehensive approach to testing that gives you confidence your code works correctly — from unit tests to mutation testing.

Core Principles

1. Test Behavior, Not Implementation

Your tests should specify what the code does, not how it does it. Tests that pass after a refactor (with the same behavior) are good tests. Tests that break after a refactor (with the same behavior) are brittle tests.

2. The Test Pyramid Is a Guideline, Not a Rule

Write many fast unit tests, some integration tests, and a few end-to-end tests. But adjust ratios based on your context: a data pipeline needs more integration tests; a UI component needs more visual regression tests.

3. Tests Are Code — Treat Them That Way

Tests need the same care as production code: clean naming, DRY helpers, proper abstractions. Test code that's hard to maintain leads to tests that get deleted.

4. Confidence Is the Goal

Coverage numbers are a proxy metric. A codebase with 80% coverage and excellent tests is better than one with 100% coverage and shallow tests. Test the things that scare you.