unclebob/crap4go

Latest recorded source activity: May 21, 2026 at 19:05

SkillsMP catalog refreshed: October 29, 2026 at 18:30

skills collected: 1

GitHub stars: 35
GitHub forks: 8

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# crap4go **CRAP** (Change Risk Anti-Pattern) metric for Go projects. Combines cyclomatic complexity with test coverage to identify functions and methods that are both complex and under-tested - the riskiest code to change. ## Quick Start Install or run with `go run`: ```bash go run github.com/unclebob/crap4go/cmd/crap4go@latest ``` From a Go module: ```bash crap4go # deletes old coverage, runs go test ./..., analyzes ``` crap4go automatically deletes stale coverage reports, runs: ```bash go test ./... -coverprofile=target/coverage/coverage.out ``` and then analyzes the results. Override the coverage test command when a project needs a narrower or tagged test invocation: ```bash crap4go --test-command "go test -tags appunit ./internal/app ./internal/sim" ``` crap4go appends `-coverprofile=target/coverage/coverage.out` to the command. If you need to control where the coverage flag appears, include `{coverprofile}` in the command: ```bash crap4go --test-command "go test ./internal/app {coverprofile} -run TestEditor" ``` Source-file analysis runs in parallel and defaults to half the available logical CPUs. Override it when needed: ```bash crap4go --max-workers 4 ``` ## Output ``` CRAP Report =========== Function Package CC Cov% CRAP ------------------------------------------------------------------------------------- Widget.Run widget 12 45.0% 130.2 simple widget 1 100.0% 1.0 ``` ## Filtering Pass module name fragments as arguments to filter: ```bash crap4go internal/combat movement # only files matching those path fragments ``` ## Coverage Mapping Notes crap4go reads Go coverage profiles from `target/coverage/coverage.out`. Coverage is matched to functions by source file and line range. If `go test` emits module-qualified source paths, crap4go also matches by path suffix so normal local paths still resolve. Files skipped during analysis: - `_test.go` files - `target/` - `vendor/` - `.git/` ## CRAP Formula ``` CRAP(fn) = CC² x (1 - coverage)³ + CC ``` - **CC** = cyclomatic complexity (decision points + 1) - **coverage** = fraction of covered Go coverage statements in the function range | Score | Risk | |-------|------| | 1-5 | Low - clean code | | 5-30 | Moderate - refactor or add tests | | 30+ | High - complex and under-tested | ## What It Counts Decision points that increase cyclomatic complexity: - `if` - `for` - `range` - `switch` and `type switch` case clauses - `select` communication clauses - `&&` - `||` ## Claude Code Skill crap4go includes a `SKILL.md` for use as a Claude Code skill. Add it to your project's `.claude/settings.json`: ```json { "skills": [ "https://github.com/unclebob/crap4go/blob/master/SKILL.md" ] } ``` Then ask Claude Code for a "CRAP report" and it will know how to set up and run the tool. ## Development ```bash go test ./... # run tests go run ./cmd/crap4go # run on own source go run ./cmd/crap4go internal/coverage # filter to one module ``` ## License Copyright (c) Robert C. Martin. All rights reserved.

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Skills in this repository

Software Quality Assurance Analysts & Testers

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crap4go

Software Quality Assurance Analysts & Testers

Use when the user asks for a CRAP report, cyclomatic complexity analysis, or code quality metrics on a Go project

2026-05-21

Showing 1 of 1 collected skill.