conventions-testing

Structure unit and integration tests by colocating test files with their source code using bun:test. Ensure behavior-driven descriptions, deterministic setup, and avoid shared mutable state to maintain consistency and reliability.

Use Playwright for browser-specific behavior such as authentication redirects, route guards, uploads, downloads, and drag-and-drop. Extract frontend logic into separate files and test it with Bun.

Prevent flaky tests by enforcing testing conventions: use plain fakes over heavy mocks, ensure deterministic setup, avoid shared mutable state, and maintain explicit, isolated test fixtures.

Yes, regression tests are required for bug fixes. Adding a regression test ensures the specific issue is covered and prevents future code changes from reintroducing the defect.

Structural invariant tests, such as auth enforcement and branded types checks, belong in the apps/api/src/tests/security/ directory. This isolates security-critical checks from general logic.

Use plain fakes instead of heavy mocks to improve test readability and maintainability. Fakes provide lightweight, deterministic setup without coupling tests tightly to implementation details.