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Testing, Quality, and Code Health
Testing, Quality, and Code Health Graphics Coverage
Primary chapter graphic: System Functionality Test Stack. Accepted graphics: 1. Reviewed non-signal pages: 1. Open graphics in review: 0. QA status lives in graphics audit and visual review ledger.
Corpus pages: p. 40-41, p. 139, p. 149-150, p. 185, p. 216-217, p. 294 Coverage: 9 pages
This chapter is part of Marius's owned architecture build corpus. The text routes decisions; durable implementation signal is carried by accepted graphics, reviewed non-signal decisions, and the linked QA audit.
Chapter Visuals
Accepted graphics carry the canonical design signal for this chapter. Each selected source page is either accepted as a graphic or explicitly marked non-signal in the source-faithful ledger. Review and QA state live in visual inventory, visual review ledger, and graphics audit.
System Functionality Test Stack
- source-page: p. 216
- batch: 30
- status: accepted
- reviewer-status: reviewed
- fidelity-score: 0.9
- spec: bbg-p0216-testing-quality-and-code-health.json
- svg: bbg-p0216-testing-quality-and-code-health.svg

Open Review Queue
- none
Reviewed Non-Signal Pages
- Testing, Quality, And Code Health: RAG + Rag Map: source p. 40; batch 31; status non-signal/reviewed; ledger reason in visual-review-ledger.json
Use When
- Change safety, regression risk, or maintainability matters more than raw delivery speed.
Avoid When
- The artifact is disposable and has no repeated use.
Core Model
- Tests and code health are feedback systems. They should cover the risks users and operators actually face.
- Prefer explicit ownership over accidental coupling. Every boundary should say who owns correctness, cost, data, recovery, and change.
- Use corpus page pointers for inspection, and keep the chapter notes focused on reusable design decisions.
Implementation Guidance
- Pair unit tests for rules with integration tests for boundaries and smoke tests for critical workflows.
- Write the smallest useful design note: purpose, inputs, outputs, state, failure behavior, observability, and rollback.
- Choose the first implementation that can be tested against the real workflow without hiding a known production risk.
Tradeoffs
- Broad tests catch integration drift but cost more to maintain.
- Centralization reduces duplicated work but can become a bottleneck when every team needs exceptions.
- Specialized infrastructure helps at scale, but it must earn its operational cost.
Failure Modes
- Mocks prove the implementation, not the behavior users rely on.
- The diagram shows boxes but not ownership, retry behavior, data freshness, or user-visible failure.
- The system has no proof path for the highest-risk assumption.
Decision Checklist
- Cover happy path, known edge case, failure mode, and one integration boundary.
- Name the owner, source of truth, timeout, retry policy, and evidence that the path works.
- Add one regression check for the failure mode most likely to recur.
Neutral Automation Examples
- A notification service tests message formatting separately from provider delivery and retry behavior.
- A neutral internal automation starts with fixtures, then adds credentials, permissions, and production scheduling only after the boundary is tested.
- A customer-facing workflow keeps irreversible actions behind explicit approval until metrics show it is safe to automate further.