dd0c: full product research pipeline - 6 products, 8 phases each

Products: route, drift, alert, portal, cost, run
Phases: brainstorm, design-thinking, innovation-strategy, party-mode,
        product-brief, architecture, epics (incl. Epic 10 TF compliance),
        test-architecture (TDD strategy)

Brand strategy and market research included.

products/05-aws-cost-anomaly/test-architecture/test-architecture.md

@@ -0,0 +1,103 @@
+# dd0c/cost — Test Architecture & TDD Strategy
+
+**Version:** 2.0  
+**Date:** February 28, 2026  
+**Status:** Authoritative  
+**Audience:** Founding engineer, future contributors
+
+---
+
+> **Guiding principle:** A cost anomaly detector that misses a $3,000 GPU instance is worse than useless — it's a liability. A cost anomaly detector that cries wolf 40% of the time gets disabled. Tests are the only way to ship with confidence at solo-founder velocity.
+
+---
+
+## Table of Contents
+
+1. [Testing Philosophy & TDD Workflow](#1-testing-philosophy--tdd-workflow)
+2. [Test Pyramid](#2-test-pyramid)
+3. [Unit Test Strategy](#3-unit-test-strategy)
+4. [Integration Test Strategy](#4-integration-test-strategy)
+5. [E2E & Smoke Tests](#5-e2e--smoke-tests)
+6. [Performance & Load Testing](#6-performance--load-testing)
+7. [CI/CD Pipeline Integration](#7-cicd-pipeline-integration)
+8. [Transparent Factory Tenet Testing](#8-transparent-factory-tenet-testing)
+9. [Test Data & Fixtures](#9-test-data--fixtures)
+10. [TDD Implementation Order](#10-tdd-implementation-order)
+
+---
+
+## 1. Testing Philosophy & TDD Workflow
+
+### Red-Green-Refactor for dd0c/cost
+
+TDD is non-negotiable for the anomaly scoring engine and baseline learning components. A scoring bug that ships to production means either missed anomalies (customers lose money) or false positives (customers disable the product). The cost of a test is minutes. The cost of a scoring bug is churn.
+
+**Where TDD is mandatory:**
+- `src/scoring/` — every scoring signal, composite calculation, and severity classification
+- `src/baseline/` — all statistical operations (mean, stddev, rolling window, cold-start transitions)
+- `src/parsers/` — every CloudTrail event parser (RunInstances, CreateDBInstance, etc.)
+- `src/pricing/` — pricing lookup logic and cost estimation
+- `src/governance/` — policy.json evaluation, auto-promotion logic, panic mode
+
+**Where TDD is recommended but not mandatory:**
+- `src/notifier/` — Slack Block Kit formatting (snapshot tests are sufficient)
+- `src/api/` — REST handlers (contract tests cover these)
+- `src/infra/` — CDK stacks (CDK assertions cover these)
+
+**Where tests follow implementation:**
+- `src/onboarding/` — CloudFormation URL generation, Cognito flows (integration tests only)
+- `src/slack/` — OAuth flows, signature verification (integration tests)
+
+### The Red-Green-Refactor Cycle
+
+```
+RED:   Write a failing test that describes the desired behavior.
+       Name it precisely: what component, what input, what expected output.
+       Run it. Watch it fail. Confirm it fails for the right reason.
+
+GREEN: Write the minimum code to make the test pass.
+       No gold-plating. No "while I'm here" refactors.
+       Run the test. Watch it pass.
+
+REFACTOR: Clean up the implementation without changing behavior.
+          Extract constants. Rename variables. Simplify logic.
+          Tests must still pass after every refactor step.
+```
+
+### Test Naming Convention
+
+All tests follow the pattern: `[unit under test] [scenario] [expected outcome]`
+
+```typescript
+// ✅ Good — precise, readable, searchable
+describe('scoreAnomaly', () => {
+  it('returns critical severity when z-score exceeds 5.0 and instance type is novel', () => {});
+  it('returns none severity when account is in cold-start and cost is below $0.50/hr', () => {});
+  it('returns warning severity when actor is novel but cost is within 2 standard deviations', () => {});
+  it('compounds severity when multiple signals fire simultaneously', () => {});
+});
+
+// ❌ Bad — vague, not searchable
+describe('scoring', () => {
+  it('works correctly', () => {});
+  it('handles edge cases', () => {});
+});
+```
+
+### Decision Log Requirement
+
+Per Transparent Factory tenet (Story 10.3), any PR touching `src/scoring/`, `src/baseline/`, or `src/detection/` must include a `docs/decisions/<YYYY-MM-DD>-<slug>.json` file. The test suite validates this in CI.
+
+```json
+{
+  "prompt": "Should Z-score threshold be 2.5 or 3.0?",
+  "reasoning": "At 2.5, false positive rate in design partner data was 28%. At 3.0, it dropped to 18% with only 2 additional missed true positives over 30 days.",
+  "alternatives_considered": ["2.0 (too noisy)", "3.5 (misses too many real anomalies)"],
+  "confidence": "medium",
+  "timestamp": "2026-02-28T10:00:00Z",
+  "author": "brian"
+}
+```
+
+---
+