cc-quality-practices

Improving quality reduces development cost. No single defect-detection technique exceeds ~75% effectiveness, so combine techniques — combining nearly doubles detection rates. Mature suites run about 5 dirty tests (error paths, bad data, edge cases) for every 1 clean test (happy path).

For active bug diagnosis (an actual failing test or repro to chase down), hand off: Skill(code-foundations:cc-debugging). This skill is for QA planning and process design.

Shared CC vocabulary and thresholds (cohesion spectrum, coupling, key metrics): Read(${CLAUDE_PLUGIN_ROOT}/references/cc-foundations.md).

External vs internal quality

• External (users care): correctness, usability, efficiency, reliability, integrity, robustness.
• Internal (developers care): maintainability, flexibility, portability, reusability, readability, testability.

Internal quality enables external quality: poor maintainability blocks fixing defects, which degrades reliability.

Defect-detection techniques (detection rate)

| Technique | Rate | Notes | |---|---|---| | Formal inspection | 45–70% | Roles, checklists, preparation. Preparation finds ~90% of the defects; the meeting adds ~10% Votta 1991]. | | Pair programming | 40–60% | Real-time review during development. | | Walk-through | 20–40% | Author-led, less structured. | | Code reading | 20–35% | Individual review emphasizing preparation. | | Unit testing | 15–50% | Developer tests of individual components. |

Modes

CHECKER

Execute the quality, review, and testing checklists against the code or process. Checklists:

• Read(${CLAUDE_SKILL_DIR}/checklists/qa-and-testing.md) — QA plan, inspections, test cases, data-flow.
• Read(${CLAUDE_SKILL_DIR}/checklists/debugging.md) — finding, fixing, brute-force, general approach.

Output one row per item: | Item | Status | Evidence | Location |, status ∈ VIOLATION (fails item) / WARNING (partial) / PASS.

APPLIER

Produce test cases, review procedures, and quality plans.

Test-case generation (output: test-case list):

1. Identify requirements → one test per requirement.
2. Compute minimum tests: 1 + count(if/while/for/and/or) + case branches (add 1 if no default case).
3. Add data-flow tests covering all defined-used paths.
4. Add boundary tests: below, at, above each boundary.
5. Add dirty tests at ~5:1 — bad data, wrong size/kind, uninitialized.
6. Add nominal tests: middle-of-road expected values.
7. Run with a coverage monitor — compare actual vs believed coverage.

Choosing a review method

| Need | Method | |---|---| | Highest defect detection (45–70%) | Formal inspection (default) | | Team geographically dispersed | Code reading (individual prep, async-friendly) | | Schedule pressure + quality | Pair programming | | Diverse viewpoints, larger group | Walk-through |

When advising a human team's review process

Inspection roles and meeting mechanics apply when designing a review process for a human team (not for solo or agent work):

1. PLANNING — moderator distributes materials with line numbers + checklist.
2. PREPARATION — each reviewer works alone using the checklist (where ~90% of defects are found).
3. MEETING — reader paraphrases the code; scribe records defects.
4. REPORT — moderator lists each defect with type and severity.
5. REWORK — author fixes defects.
6. FOLLOW-UP — moderator verifies all fixes complete.

Chain

| After | Next | |---|---| | Defect to fix found | Skill(code-foundations:cc-refactoring-guidance) | | Design issues found | Skill(code-foundations:cc-routine-and-class-design) | | Active bug to diagnose | Skill(code-foundations:cc-debugging) |