| name | code-quality-crap |
| description | CRAP score quality gate for code complexity and test coverage. Use when reviewing methods for complexity risk, deciding whether to split methods, or determining minimum test coverage requirements. |
Code Quality: CRAP Score
CRAP (Change Risk Anti-Patterns) measures the risk of a method based on
cyclomatic complexity and test coverage.
When to Use
- Reviewing new or changed methods for complexity risk
- Deciding whether a method needs splitting
- Determining minimum test coverage for a given complexity
- During TDD Refactor phase to validate structural improvements
Formula
$$\text{CRAP}(m) = \text{comp}(m)^2 \times (1 - \text{cov}(m))^3 + \text{comp}(m)$$
Where:
- $\text{comp}(m)$ = cyclomatic complexity of method $m$
- $\text{cov}(m)$ = test coverage ratio (0 to 1) of method $m$
Quality Gate
Every method MUST have a CRAP score below 6.
Coverage Thresholds
These thresholds are intentionally stricter than the mathematical minimum,
providing a safety margin:
| Complexity | Recommended coverage for CRAP < 6 |
|---|
| 1 | 0% (any) |
| 2 | > 0% |
| 3 | 40%+ |
| 4 | 60%+ |
| 5 | 80%+ |
| 6+ | Not achievable: must split to reduce complexity |
Actions by Scenario
| Scenario | Action |
|---|
| CRAP >= 6 due to high complexity | Extract complex branches into smaller methods |
| CRAP >= 6 due to low coverage | Add tests (new Red/Green cycle) |
| Complexity 6+ regardless of coverage | Must split: CRAP floor equals complexity |
Severity Classification
- Medium: complexity 4–5 without proportional test coverage
- High: complexity 6+ (must split, no amount of testing fixes it)
