Mutation Check
SkillDev toolsLets your agent run mutation testing on changed Rust code and keep the mutant config file up to date.
Instructions available. Your AI can read the instructions. Execution depends on the setup they require.
Account requirements not reviewed. Check the skill instructions before use; ahel provides instructions and does not run this skill.
Add ahel to your AI once: Claude, ChatGPT, Cursor, Claude Code or Codex. Then ask it to use this.
Then ask your AI: use the Mutation Check skill
About this skill
Run cargo-mutants for changed coop logic and keep .cargo/mutants.toml synchronized. Use when logic-dense modules change, before refactors, or when asked to verify mutation coverage.
What this skill tells your AI
The instructions your AI receives, as published by trailofbits/coop in .agents/skills/mutation-check/SKILL.md and read by ahel’s review.
Read docs/testing.md first.
- Inspect the diff before running. New functions in logic modules that shell
out, drive
&PlatformBackend, read a TTY, or write stdout must be excluded in.cargo/mutants.tomlin the same PR. Extract and test their pure decision logic. Pure helpers remain in scope. - Sanity-check changed exclusions with
cargo mutants --list -f <file>. - Run a full-file sweep for each touched scoped module and library tests only:
cargo mutants -f src/<file>.rs -- --lib. Redirect output to a file; do not pipe a long run throughheadorgrep. - Triage
mutants.out/missed.txt: add a discriminating test for real gaps, mark genuinely equivalent mutants with a narrow documented skip, and delete dead code. Confirm each new test by re-running the mutant or deliberately breaking the protected behavior. - Report files swept, missed count before/after, every survivor's disposition,
and whether
.cargo/mutants.tomlchanged.
Do not spend a full mutation run on whole-module exclusions (backend.rs,
lima.rs, setup.rs, update.rs, ssh.rs, vm.rs, network.rs,
port_forward.rs, cmd.rs, prompt.rs, main.rs). Instead, identify the
unit/integration blind spot explicitly and test extracted pure logic directly.
Signals
- GitHub stars
- 740
- Forks
- 38
- Last commit
- Oct 2026
Advanced
- Item type
- skill
- Key
mutation-check- Source
- github.com/trailofbits/coop