code-quality-crap

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)