Mutineer

On the record

Coverage

Per test coverage can select which tests to run for each mutant, and covered line filtering requires a coverage file.github.com · read 8 Oct 2026

How it works

It checks a baseline test run, applies AST safe mutations to source files, runs tests that import the changed file, and reports kill rates and escaped mutants.github.com · read 8 Oct 2026

Installation requirement

The package is installed with npm and its package metadata requires Node.js 20 or later.github.com · read 8 Oct 2026

Language support

It supports TypeScript and JavaScript modules and Vue single file components using script setup.github.com · read 8 Oct 2026

Large repositories

The project warns that full codebase runs may take a while and recommends incremental strategies for large repositories.github.com · read 8 Oct 2026

License

The project is published under the MIT license.github.com · read 8 Oct 2026

Maintainer

The repository lists Billy Jones as a maintainer.github.com · read 8 Oct 2026

Mutation handling

Mutations use Babel AST analysis so operators in strings and comments are not changed.github.com · read 8 Oct 2026

Mutation process

It runs a baseline test suite, mutates source files with AST safe operator replacements, reruns relevant tests, and reports kill rates and escaped mutants.github.com · read 8 Oct 2026

Mutation safety

Mutations use Babel AST analysis, so operators inside strings and comments are not changed.github.com · read 8 Oct 2026

Package availability

The package page lists the installation command as npm i @mutineerjs/mutineer.npmjs.com · read 8 Oct 2026

Purpose

Mutineer is a mutation testing framework for JavaScript and TypeScript that changes source code and runs existing tests to reveal defects the tests miss.github.com · read 8 Oct 2026

Reports

The CLI supports text and JSON reports, with JSON written to mutineer-report.json.github.com · read 8 Oct 2026

Scoping options

Runs can be scoped to changed files, changed files and their local imports, or lines covered by tests.github.com · read 8 Oct 2026

Targeted runs

The CLI can limit mutation runs to changed files, changed files and their imports, or code on covered lines.github.com · read 8 Oct 2026

Test runners

It is built for Vitest, has first class Jest support, and allows other test runners through an adapter interface.github.com · read 8 Oct 2026

Alternatives to Mutineer

A ArcMutateWindowsMac+2 M MutantMacLinux M MutatestWindowsMac+3 M MuJavaWindowsMac+1 G GambitWindowsMac+1 I InfectionWebMac+1 M mutmutWindowsMac+2 M muttestWindowsMac+1

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