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. When its CHECKER surfaces a design smell, hand off to Skill(code-foundations:cc-routine-and-class-design); when a fix needs restructuring, to Skill(code-foundations:cc-refactoring-guidance).

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: Read(${CLAUDE_SKILL_DIR}/checklists.md) — QA plan, inspections, pair programming, test cases, data-flow. For debugging checklists (finding, fixing, syntax errors, brute force) invoke Skill(code-foundations:cc-debugging) — they live there, not here.

VIOLATION = fails the item; WARNING = partial. CHECKER output: the ID'd checklist is the item set (the tables in this SKILL.md explain the items, they are not counted twice). Report each VIOLATION and WARNING as | Item | Status | Evidence | Location |; do not list passing or non-applicable items — close with one line N items checked, M pass, K n/a.

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 (not the author) 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.