mutator

Spec sheet

Purpose

mutator is an automated mutation testing tool for the R language that checks whether a test suite detects systematic changes to source code.Read 7 Oct 2026 · pdonatbouillud.com

Intended users

The maker describes it for developers who want to assess the quality of R package test suites.Read 7 Oct 2026 · github.com

Support

The documentation links to a GitHub page for reporting bugs.Read 7 Oct 2026 · prl-prg.github.io

License

The package is licensed under GPL (>= 3).Read 7 Oct 2026 · prl-prg.github.io

AST mutations

mutator applies mutations at the abstract syntax tree level.Read 7 Oct 2026 · pdonatbouillud.com

CI integration

It provides a reusable GitHub Actions workflow for mutation testing, including optional mutation-score thresholds and badge publishing.Read 7 Oct 2026 · prl-prg.github.io

Developers

The project is developed by Pierre Donat-Bouillud and Assanali Amandykov.Read 7 Oct 2026 · prl-prg.github.io

Equivalent mutants

It can use LLMs to flag likely equivalent mutants through a configurable OpenAI-compatible API.Read 7 Oct 2026 · prl-prg.github.io

Execution speed

It supports parallel test execution and coverage-guided selection that runs only tests covering each mutated line.Read 7 Oct 2026 · pdonatbouillud.com

Installation

The released version can be installed from CRAN with install.packages("mutator"), and development versions are available from GitHub and R-universe.Read 7 Oct 2026 · prl-prg.github.io

Limits and configuration

Users can cap the number of mutants and set a per-mutant timeout; coverage-guided selection falls back to the full suite for the generic installed-tests strategy.Read 7 Oct 2026 · prl-prg.github.io

LLM integration

Equivalent-mutant detection can use an OpenAI-compatible API.Read 7 Oct 2026 · prl-prg.github.io

Mutation method

It uses abstract syntax tree analysis and mutation operators for arithmetic, comparisons, logic, constants, return values, and statement deletion.Read 7 Oct 2026 · prl-prg.github.io

Mutation operators

Its operators include arithmetic, comparison and logical changes, constant and return-value replacements, and statement deletions.Read 7 Oct 2026 · pdonatbouillud.com

Mutation score

It reports the ratio of killed mutants to total mutants as a measure of test suite effectiveness.Read 7 Oct 2026 · pdonatbouillud.com

Notable limit

Coverage-guided selection is on by default for testthat and tinytest strategies; with the generic installed-tests fallback, it warns and runs the full suite.Read 7 Oct 2026 · prl-prg.github.io

Performance

It supports parallel test execution and coverage-guided test selection, which runs tests covering each mutated line.Read 7 Oct 2026 · prl-prg.github.io

Test harnesses

It supports testthat and tinytest, with a generic installed-tests fallback for other layouts.Read 7 Oct 2026 · prl-prg.github.io

Timeouts

It self-calibrates per-mutant timeouts to detect hangs, and users can override the timeout.Read 7 Oct 2026 · prl-prg.github.io

Where Specifiction places it

• Mutation Testing Tools#21 of 256.9