Testing: Write Tests That Catch Real Bugs

Write, structure, and maintain tests across unit, integration, E2E, accessibility, and performance layers. The goal is tests that catch regressions, document behavior, and run fast in CI - not tests that exist to inflate coverage numbers.

Target versions: see references/versions.md (verified per the receipt date in that file). Do not restate version numbers here.

When to use

• Writing new tests (unit, integration, E2E, accessibility, performance)
• Debugging flaky or failing tests
• Designing test architecture for a project (fixture strategies, factory patterns, test data)
• Setting up test infrastructure in CI (parallelization, sharding, coverage gates)
• Choosing testing tools or migrating between test frameworks
• Choosing the smallest test set that protects a change
• Adding accessibility or visual regression tests to an existing suite

When NOT to use