implement

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• SKILL.md

SKILL.md (first lines)

# Implement

Implement one ticket. This is the per-ticket implementation cycle,
called by wayfinder for each ticket in the breakdown.

## Process

1. **Confirm the ticket is unblocked** — its dependencies (if tracked)
   are done. If not, report back to wayfinder to pick a different one.

2. **Red.** Write a failing test at a pre-agreed seam (public
   interface). Confirm it fails for the expected reason, not an
   unrelated error.

3. **Green.** Write the smallest honest implementation that makes the
   test pass. No hardcoding expected output.

4. **Type check** regularly throughout implementation.

5. **Run tests** — the specific test file as you work, then a full
   test sweep at the end. **Evidence gate:** the ticket is not done until
   you paste the actual green test/command output. Asserting "tests pass"
   without the output does not advance the ticket.

6. **Invoke `skills/code-review/SKILL.md`** to review the work.

7. **Commit** the work to the current branch. One commit per completed
   ticket with a message describing what it delivers.

8. **Update tracking** — mark the ticket as done in the configured
   tracker.

## TDD discipline

Uses `/codebase-design` vocabulary for seam placement: accept
dependencies don't create them; place seams at volatile boundaries;
the interface is the test surface.

- **Tests verify behavior through seams** — pre-agreed public
  interfaces and boundaries. Never test implementation internals.
- **Red before green.** No implementation before its test exists and
  fails for the right reason.
- **Green means smallest honest implementation.** No stubbing the
  behavior under test.

Reference: `skills/tdd/SKILL.md` for the full TDD
discipline (red→green, anti-patterns).

## Anti-patterns (never do these)

- Implementation-coupled tests (testing private methods, internal state).
- Tautological assertions (mock wired to be called, then asserted).
- Horizontal slicing within a ticket.
- Skipping the code-review step.

## Bundled skill references

- `skills/tdd/SKILL.md` — TDD discipline reference
- `skills/codebase-design/SKILL.md` — vocabulary for seam
  placement and interface depth

## What this skill must never do

- Never skip tests at agreed seams.
- Never commit without the full test sweep passing.
- Never skip code review before committing.
- Never write a test that can't actually fail.

From lynchypin/project-onboard, MIT.

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