Mutineer
github.com
Spec sheet
- 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.Read 8 Oct 2026 · github.com
- License
- The project is published under the MIT license.Read 8 Oct 2026 · github.com
- Coverage
- Per test coverage can select which tests to run for each mutant, and covered line filtering requires a coverage file.Read 8 Oct 2026 · github.com
- 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.Read 8 Oct 2026 · github.com
- Installation requirement
- The package is installed with npm and its package metadata requires Node.js 20 or later.Read 8 Oct 2026 · github.com
- Language support
- It supports TypeScript and JavaScript modules and Vue single file components using script setup.Read 8 Oct 2026 · github.com
- Large repositories
- The project warns that full codebase runs may take a while and recommends incremental strategies for large repositories.Read 8 Oct 2026 · github.com
- Maintainer
- The repository lists Billy Jones as a maintainer.Read 8 Oct 2026 · github.com
- Mutation handling
- Mutations use Babel AST analysis so operators in strings and comments are not changed.Read 8 Oct 2026 · github.com
- 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.Read 8 Oct 2026 · github.com
- Mutation safety
- Mutations use Babel AST analysis, so operators inside strings and comments are not changed.Read 8 Oct 2026 · github.com
- Package availability
- The package page lists the installation command as npm i @mutineerjs/mutineer.Read 8 Oct 2026 · npmjs.com
- Reports
- The CLI supports text and JSON reports, with JSON written to mutineer-report.json.Read 8 Oct 2026 · github.com
- Scoping options
- Runs can be scoped to changed files, changed files and their local imports, or lines covered by tests.Read 8 Oct 2026 · github.com
- Targeted runs
- The CLI can limit mutation runs to changed files, changed files and their imports, or code on covered lines.Read 8 Oct 2026 · github.com
- Test runners
- It is built for Vitest, has first class Jest support, and allows other test runners through an adapter interface.Read 8 Oct 2026 · github.com
Where Specifiction places it
- Mutation Testing Tools#24 of 256.5
