GOOS-Style TDD for AdonisJS v7

Philosophy

Core principle: Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't.

Good tests are integration-style: they exercise real code paths through public APIs. They describe what the system does, not how it does it. A good test reads like a specification — "authenticated user can create a post" tells you exactly what capability exists. These tests survive refactors because they don't care about internal structure.

Bad tests are coupled to implementation. They mock internal collaborators, test private methods, or verify through external means (like querying the database directly instead of using the API). The warning sign: your test breaks when you refactor, but behavior hasn't changed.

Develop from inputs to outputs: Work outside-in — start from the external event (HTTP request, browser action) and let each test drive you inward through the layers. The acceptance test defines the entry point; inner-loop tests discover the services and collaborators needed to fulfill it. Don't start from the database schema or model layer and build outward.

See tests.md for examples and mocking.md for mocking guidelines.

Anti-Pattern: Horizontal Slices

DO NOT write all tests first, then all implementation. This is "horizontal slicing" — treating RED as "write all tests" and GREEN as "write all code."