tdd: drop the refactor stage — red → green, not red → green → refactor

Refactoring belongs to the review stage, not the implementation loop.
Remove the refactor rule and the now-orphaned refactoring.md (its home is
the review skill), and point the loop's rule at the review skill so it
isn't re-added.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.changeset/tdd-reference-only-seams.md

@@ -0,0 +1,7 @@
+---
+"mattpocock-skills": patch
+---
+
+Reshape the `tdd` skill into reference-only. The red → green → refactor loop is anchored by leading words the model already holds, so the step-by-step Workflow was largely restating the loop and duplicating the horizontal-slicing anti-pattern. Dropped the Workflow and per-cycle checklist; folded their one durable idea — vertical slices / tracer bullets — into the Anti-patterns section and a short Rules-of-the-loop list. Introduced **seam** as the leading word for where tests go, collapsing the old Philosophy "public interfaces" prose and the Planning "confirm interface / behaviors" handshake into one rule: test only at pre-agreed seams, confirmed with the user before any test is written.
+
+Also dropped the refactor stage — TDD is now red → green, not red → green → refactor. Refactoring belongs to the review stage, not the implementation loop, so the refactor rule and `refactoring.md` were removed (its home is the `review` skill).

.changeset/tdd-tautological-tests.md

@@ -0,0 +1,5 @@
+---
+"mattpocock-skills": patch
+---
+
+Add the **tautological test** anti-pattern to the `tdd` skill. Tests whose assertion is recomputed the way the code computes it pass by construction and give zero confidence — distinct from the implementation-coupling anti-pattern already covered. Added as a peer at the same three sites: a Philosophy principle (expected values must come from an independent source of truth), a per-cycle checklist gate, and a BAD/GOOD example pair in `tests.md`.

skills/engineering/tdd/SKILL.md

@@ -5,104 +5,32 @@ description: Test-driven development. Use when the user wants to build features
 
 # Test-Driven Development
 
-## Philosophy
+TDD is the red → green loop. This skill is the reference that makes that loop produce tests worth keeping: what a good test is, where tests go, the anti-patterns, and the rules of the loop. Every section applies on every cycle — consult them before and during the loop, not after.
 
-**Core principle**: Tests should verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't.
+When exploring the codebase, read `CONTEXT.md` (if it exists) so test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.
 
-**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 - "user can checkout with valid cart" tells you exactly what capability exists. These tests survive refactors because they don't care about internal structure.
+## What a good test is
 
-**Bad tests** are coupled to implementation. They mock internal collaborators, test private methods, or verify through external means (like querying a database directly instead of using the interface). The warning sign: your test breaks when you refactor, but behavior hasn't changed. If you rename an internal function and tests fail, those tests were testing implementation, not behavior.
+Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification — "user can checkout with valid cart" tells you exactly what capability exists — and survives refactors because it doesn't care about internal structure.
 
 See [tests.md](tests.md) for examples and [mocking.md](mocking.md) for mocking guidelines.
 
-## Anti-Pattern: Horizontal Slices
+## Seams — where tests go
 
-**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."
+A **seam** is the public boundary you test at: the interface where you observe behavior without reaching inside. Tests live at seams, never against internals.
 
-This produces **crap tests**:
+**Test only at pre-agreed seams.** Before writing any test, write down the seams under test and confirm them with the user. No test is written at an unconfirmed seam. You can't test everything — agreeing the seams up front is how testing effort lands on the critical paths and complex logic instead of every edge case.
 
-- Tests written in bulk test _imagined_ behavior, not _actual_ behavior
+Ask: "What's the public interface, and which seams should we test?"
-- You end up testing the _shape_ of things (data structures, function signatures) rather than user-facing behavior
-- Tests become insensitive to real changes - they pass when behavior breaks, fail when behavior is fine
-- You outrun your headlights, committing to test structure before understanding the implementation
 
-**Correct approach**: Vertical slices via tracer bullets. One test → one implementation → repeat. Each test responds to what you learned from the previous cycle. Because you just wrote the code, you know exactly what behavior matters and how to verify it.
+## Anti-patterns
 
-```
+- **Implementation-coupled** — mocks internal collaborators, tests private methods, or verifies through a side channel (querying the database instead of using the interface). The tell: the test breaks when you refactor but behavior hasn't changed.
-WRONG (horizontal):
+- **Tautological** — the assertion recomputes the expected value the way the code does (`expect(add(a, b)).toBe(a + b)`, a snapshot derived by hand the same way, a constant asserted equal to itself), so it passes by construction and can never disagree with the code. Expected values must come from an independent source of truth — a known-good literal, a worked example, the spec.
-  RED:   test1, test2, test3, test4, test5
+- **Horizontal slicing** — writing all tests first, then all implementation. Bulk tests verify _imagined_ behavior: you test the _shape_ of things rather than user-facing behavior, the tests go insensitive to real changes, and you commit to test structure before understanding the implementation. Work in **vertical slices** instead — one test → one implementation → repeat, each test a **tracer bullet** that responds to what the last cycle taught you.
-  GREEN: impl1, impl2, impl3, impl4, impl5
 
-RIGHT (vertical):
+## Rules of the loop
-  RED→GREEN: test1→impl1
-  RED→GREEN: test2→impl2
-  RED→GREEN: test3→impl3
-  ...
-```
 
-## Workflow
+- **Red before green.** Write the failing test first, then only enough code to pass it. Don't anticipate future tests or add speculative features.
-
+- **One slice at a time.** One seam, one test, one minimal implementation per cycle.
-### 1. Planning
+- **Refactoring is not part of the loop.** It belongs to the review stage (see the `review` skill), not the red → green implementation cycle.
-
-When exploring the codebase, read `CONTEXT.md` (if it exists) so that test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.
-
-Before writing any code:
-
-- [ ] Confirm with user what interface changes are needed
-- [ ] Confirm with user which behaviors to test (prioritize)
-- [ ] Identify opportunities for deep modules (small interface, deep implementation) — run the `/codebase-design` skill for the vocabulary and the testability checks
-- [ ] List the behaviors to test (not implementation steps)
-- [ ] Get user approval on the plan
-
-Ask: "What should the public interface look like? Which behaviors are most important to test?"
-
-**You can't test everything.** Confirm with the user exactly which behaviors matter most. Focus testing effort on critical paths and complex logic, not every possible edge case.
-
-### 2. Tracer Bullet
-
-Write ONE test that confirms ONE thing about the system:
-
-```
-RED:   Write test for first behavior → test fails
-GREEN: Write minimal code to pass → test passes
-```
-
-This is your tracer bullet - proves the path works end-to-end.
-
-### 3. Incremental Loop
-
-For each remaining behavior:
-
-```
-RED:   Write next test → fails
-GREEN: Minimal code to pass → passes
-```
-
-Rules:
-
-- One test at a time
-- Only enough code to pass current test
-- Don't anticipate future tests
-- Keep tests focused on observable behavior
-
-### 4. Refactor
-
-After all tests pass, look for [refactor candidates](refactoring.md):
-
-- [ ] Extract duplication
-- [ ] Deepen modules (move complexity behind simple interfaces)
-- [ ] Apply SOLID principles where natural
-- [ ] Consider what new code reveals about existing code
-- [ ] Run tests after each refactor step
-
-**Never refactor while RED.** Get to GREEN first.
-
-## Checklist Per Cycle
-
-```
-[ ] Test describes behavior, not implementation
-[ ] Test uses public interface only
-[ ] Test would survive internal refactor
-[ ] Code is minimal for this test
-[ ] No speculative features added
-```

skills/engineering/tdd/refactoring.md

@@ -1,10 +0,0 @@
-# Refactor Candidates
-
-After TDD cycle, look for:
-
-- **Duplication** → Extract function/class
-- **Long methods** → Break into private helpers (keep tests on public interface)
-- **Shallow modules** → Combine or deepen
-- **Feature envy** → Move logic to where data lives
-- **Primitive obsession** → Introduce value objects
-- **Existing code** the new code reveals as problematic

skills/engineering/tdd/tests.md

@@ -59,3 +59,19 @@ test("createUser makes user retrievable", async () => {
   expect(retrieved.name).toBe("Alice");
 });
 ```
+
+**Tautological tests**: Expected value restates the implementation, so the test passes by construction.
+
+```typescript
+// BAD: Expected value is recomputed the way the code computes it
+test("calculateTotal sums line items", () => {
+  const items = [{ price: 10 }, { price: 5 }];
+  const expected = items.reduce((sum, i) => sum + i.price, 0);
+  expect(calculateTotal(items)).toBe(expected);
+});
+
+// GOOD: Expected value is an independent, known literal
+test("calculateTotal sums line items", () => {
+  expect(calculateTotal([{ price: 10 }, { price: 5 }])).toBe(15);
+});
+```

skills/in-progress/decision-mapping/SKILL.md

@@ -14,12 +14,14 @@ Assets created during tickets should be linked to from the map, not duplicated w
 
 ### Structure
 
-Numbered entries ("tickets"), each its own section keyed by its number:
+Entries ("tickets"), each its own section keyed by a short dash-case slug that
+reads as a mini-title (e.g. `relational-db`, `auth-strategy`, `cache-layer`) —
+terse enough to stay token-efficient, and unique within the map.
 
 ```markdown
-## #1: Relational Or Non-Relational Database?
+## relational-db: Relational Or Non-Relational Database?
 
-Blocked by: #<ticket-number>, #<ticket-number>
+Blocked by: <slug>, <slug>
 Status: open | in-progress | resolved
 Type: Research | Prototype | Grilling
 
@@ -32,7 +34,11 @@ Type: Research | Prototype | Grilling
 <answer-here>
 ```
 
-A ticket is **unblocked** when every ticket in its `Blocked by` list is `resolved`. A session **claims** its ticket by setting `Status: in-progress` and saving the map before any work, so concurrent sessions skip it.
+The slug is the canonical id, used in every `Blocked by` edge and prose
+reference; the title after the colon is optional. A ticket
+is **unblocked** when every ticket in its `Blocked by` list is `resolved`. A
+session **claims** its ticket by setting `Status: in-progress` and saving the map
+before any work, so concurrent sessions skip it.
 
 Each ticket must be sized to one 100K token agent session.
 
@@ -62,10 +68,10 @@ User invokes with a loose idea.
 
 ### Work through the map
 
-User invokes with a path to an existing map. A ticket number is **optional** — without one, you pick the next decision, not the user.
+User invokes with a path to an existing map. A ticket slug is **optional** — without one, you pick the next decision, not the user.
 
 1. Load the **whole map** as context.
-2. Choose the ticket. If the user named one, use it. Otherwise pick the lowest-numbered `open` ticket that is [unblocked](#structure). [Claim it](#structure): set `Status: in-progress` and save before any work.
+2. Choose the ticket. If the user named one, use it. Otherwise pick the first `open` ticket in document order that is [unblocked](#structure). [Claim it](#structure): set `Status: in-progress` and save before any work.
 3. Resolve it, invoking skills as needed. If in doubt, use `/grilling` and `/domain-modeling`.
 4. Record the answer in the ticket's body and set `Status: resolved`.
 5. Add newly-discovered tickets with correct `Blocked by` edges. If the decisions made invalidate other parts of the map, update or delete those nodes.
@@ -79,7 +85,7 @@ End every session by clearing the context and opening one or more fresh sessions
 
 **Open tickets remain.** List the currently-unblocked tickets, then give two copy-paste options: a bare command for one session (you pick the next ticket), and one pinned command per unblocked ticket for running them in parallel. Paste one line per fresh window — opening one, some, or all of them.
 
-> **Next steps** — 3 tickets unblocked: #4, #5, #6.
+> **Next steps** — 3 tickets unblocked: `auth-strategy`, `cache-layer`, `rate-limits`.
 > Clear the context, then open fresh sessions.
 >
 > **One session** — resolves the next unblocked ticket:
@@ -89,9 +95,9 @@ End every session by clearing the context and opening one or more fresh sessions
 >
 > **Parallel** — paste one line per window, up to all 3:
 > ```
-> Invoke /decision-mapping with the map at <path>, ticket #4.
+> Invoke /decision-mapping with the map at <path>, ticket auth-strategy.
-> Invoke /decision-mapping with the map at <path>, ticket #5.
+> Invoke /decision-mapping with the map at <path>, ticket cache-layer.
-> Invoke /decision-mapping with the map at <path>, ticket #6.
+> Invoke /decision-mapping with the map at <path>, ticket rate-limits.
 > ```
 
 **No open tickets remain.** The fog is pushed back far enough that the path to the finish line is clear — the map is done. (The initial grilling may also surface no fog at all, in which case there was never a map to build.) Recommend implementing directly, or using `/to-prd` to schedule a multi-session implementation.