# Mutation-CRAP

Experimental metric `mutation-crap` version 1, status policy `timeouts-killed-v1`: `C² × (1 − MS)³ + C` with C the JaCoCo complexity and MS the share of killed mutants, as the policy counts them.
No threshold is proven; a score is no proof of correctness.

- Analysis: `:pitest`
- Tools: werkcrappit 0.26.10, PIT 1.30.0, JaCoCo 0.8.15
- Scope: 3 classes selected by PIT, all read

## Summary

| State | Methods |
| --- | ---: |
| SCORED | 2 |
| NO_MUTATION_RESULTS | 1 |
| NO_ELIGIBLE_MUTANTS | 1 |
| INCONCLUSIVE | 1 |
| COMPLEXITY_UNAVAILABLE | 1 |
| EXCLUDED | 1 |

## Scored Methods

Highest score first.

| Mutation-CRAP | Complexity | Mutation score | Killed / eligible | Method |
| ---: | ---: | ---: | ---: | --- |
| 22.5 | 10 | 0.50 | 5 / 10 | `demo.Classifier.classify(I)Ljava/lang/String;` |
| 1 | 1 | 1.00 | 1 / 1 | `demo.Classifier.normalize(I)I` |

## Methods Without Score

These are not rated well or badly; they have no score, for the reasons given.

| State | Method | Complexity | Mutants | Reasons |
| --- | --- | ---: | --- | --- |
| NO_ELIGIBLE_MUTANTS | `demo.Classifier.compare(II)I` | 2 | NON_VIABLE 2 | `no-eligible-mutants` |
| NO_MUTATION_RESULTS | `demo.Classifier.describe()Ljava/lang/String;` | 2 | none | `no-mutation-results` |
| INCONCLUSIVE | `demo.Classifier.retry(I)I` | 3 | KILLED 2, RUN_ERROR 1 | `inconclusive-status:RUN_ERROR` |
| EXCLUDED | `demo.Grade.values()[Ldemo/Grade;` | — | none | `jacoco-filtered:other` |
| COMPLEXITY_UNAVAILABLE | `demo.Legacy.run()V` | — | SURVIVED 1 | `complexity-unavailable`, `method-not-in-inventory` |

## Cohesion and Coupling

LCOM4 counts groups of methods that neither call each other nor share a field; above 1, a class could be split.
Ce counts the other classes of the analysed code a class depends on, Ca those depending on it.

| LCOM4 | Class | Method groups |
| ---: | --- | --- |
| 2 | `demo.Classifier` | classify, normalize, retry · compare, describe |

| Ce | Ca | Class |
| ---: | ---: | --- |
| 1 | 0 | `demo.Classifier` |
| 0 | 1 | `demo.Grade` |

## Change Risk

Mutation-CRAP over the whole class, its scored methods summed, times (1 + (LCOM4 - 1) / 2) times (1 + Ce / 20).
A class with an unclear method or without a scored one has no change risk.

| Change risk | Complexity | Mutation score | Killed / eligible | LCOM4 | Ce | Class |
| ---: | ---: | ---: | ---: | ---: | ---: | --- |

## Exclusion Rules

- PIT `excludedMethods`: none
- werkcrappit `excludeClasses`: none
- werkcrappit `excludeMethods`: none
- Methods JaCoCo filters as compiler-generated are excluded with the reason `jacoco-filtered:…`.