docs(phase-2): add validation strategy

.planning/phases/02-authentication/02-VALIDATION.md

@@ -0,0 +1,83 @@
+---
+phase: 2
+slug: authentication
+status: draft
+nyquist_compliant: false
+wave_0_complete: false
+created: 2026-05-14
+---
+
+# Phase 2 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | Go `testing` + `go test` (stdlib) |
+| **Config file** | `backend/go.mod` (no separate config) |
+| **Quick run command** | `cd backend && go test ./internal/auth/...` |
+| **Full suite command** | `cd backend && go test ./...` |
+| **Estimated runtime** | ~15–30 seconds (argon2 tests use reduced params) |
+
+DB-touching tests require `TEST_DATABASE_URL` pointing at the compose-managed Postgres (see Phase 1 pattern in `backend/internal/db/pool_test.go`). Each test runs in a transaction that rolls back, OR uses a per-test schema name to avoid cross-contamination.
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Run `go test ./internal/auth/...`
+- **After every plan wave:** Run `go test ./...`
+- **Before `/gsd-verify-work`:** Full suite must be green
+- **Max feedback latency:** 30 seconds
+
+---
+
+## Per-Task Verification Map
+
+Filled by planner as PLAN.md tasks are emitted. Each task with `type: execute` must have an `<automated>` verify command OR an explicit Wave 0 dependency. Tasks creating templ/HTML output may need a small Go test that renders the component and asserts the resulting HTML contains expected markers.
+
+| Task ID | Plan | Wave | Requirement | Threat Ref | Secure Behavior | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|------------|-----------------|-----------|-------------------|-------------|--------|
+| (to be filled by planner) | | | | | | | | | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+- [ ] `backend/internal/auth/password_test.go` — argon2 hash/verify round-trip with reduced test params
+- [ ] `backend/internal/auth/session_test.go` — token generate + SHA-256 lookup, expiry semantics
+- [ ] `backend/internal/auth/ratelimit_test.go` — per-key bucket allow/deny with injectable clock
+- [ ] `backend/internal/auth/middleware_test.go` — ResolveSession context plumbing, RequireAuth 303 / HX-Redirect
+- [ ] Reuse `backend/internal/db/pool_test.go` Postgres harness for users/sessions integration tests
+
+*Existing Go test infrastructure (Phase 1) covers framework setup — no new tooling install needed.*
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| Cookie is `HttpOnly` and `Secure` in non-dev environments | AUTH-03 | Browser DevTools required to inspect cookie attributes from a live response | Run `ENV=staging` server, hit `/login`, submit valid creds, open DevTools → Application → Cookies; confirm `HttpOnly=true`, `Secure=true`, `SameSite=Lax` |
+| `/login` page visual layout matches Phase 1 design system | AUTH-01 / D-69 | Visual assertion | Open `http://localhost:8080/login`, confirm Button/Card/Badge styling from `internal/web/ui` is applied; confirm `/signup` mirrors |
+| HTMX inline form-error swap on bad credentials | AUTH-02 | Requires browser to evaluate `HX-Request` round-trip | Submit `/login` with bad password via HTMX form; only the form fragment swaps with "Invalid email or password" — no full page reload |
+| Rate-limit error fragment shows after 6th failed login | AUTH-06 | Requires browser to observe 429 + swap | Submit 6 wrong-password attempts in <60s from same IP; 6th returns 429 with "Too many attempts" inline fragment |
+
+---
+
+## Validation Sign-Off
+
+- [ ] All tasks have `<automated>` verify or Wave 0 dependencies
+- [ ] Sampling continuity: no 3 consecutive tasks without automated verify
+- [ ] Wave 0 covers all MISSING references
+- [ ] No watch-mode flags
+- [ ] Feedback latency < 30s
+- [ ] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending