tdd
Installation
SKILL.md
Test-Driven Development
Iron Law
No prod code without failing test first. No exceptions.
Test seams and anti-patterns
- Seams: test at public boundaries. Before a test, write down the seam and confirm pre-agreed seams with the user when the issue or existing convention does not make it obvious. No tests at unconfirmed internals.
- Tautological tests: do not recompute expected values the same way code does; use an independent source of truth: known-good literal, worked example, fixture, spec, or observed behavior.
- Horizontal slices: do not write all tests first, then all impl. Bulk tests test imagined behavior. Correct: vertical slices -- one RED->GREEN test+impl, then repeat.
State Machine
Full state diagram: REFERENCE.md#state-machine.