Mutant

Mac · Linux · paid plans from $20.83/mo

Freedom report

Two barsScore 6.5

Free tierA free tier is on its own pricing page
Open codeNo open-source code on record
Runs widely2 of 6 device platforms
DocumentedPlans, terms and facts published

Mutant is ranked #2 of 25 in mutation testing tools on Freedom251. It runs on Linux, macOS. There is a free plan. Paid plans start at $20.83/mo.

Mutant plans and pricing

All plans

Open source Free public repositories · full feature set github.com · 1 Oct 2026

Commercial monthly $30/mo per developer any number of repositories · CI use requires no additional subscriptions github.com · 1 Oct 2026

Commercial yearly $250/yr per developer any number of repositories · CI use requires no additional subscriptions github.com · 1 Oct 2026

Enterprise Not published volume subscriptions · custom plans github.com · 1 Oct 2026

Compared on mutation testing tools

Free plan: Yes
Paid from: $30/mo
Supported languages: Ruby
Test frameworks: RSpec, Minitest, Test::Unit
Incremental analysis: Yes
Parallel execution: Yes
Surviving mutant reports: Yes
Mutation operators: Arithmetic, logical, bitwise, statement removal, return-value modification, ordering

Best Mutant alternatives

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Two bars ArcMutate Free tier No. 1$8/mo6.6 Two bars Mutatest Free tier No. 3Free6.5 One bar Stryker Mutator Free tier No. 4Free6.3 One bar Infection Paid plans No. 5—5.6 One bar muttest Paid plans No. 6—5.6 One bar PIT Paid plans No. 7—5.6

The record

Purpose: Mutant is mutation testing for Ruby that systematically modifies code and verifies that tests catch each change.
Test integrations: Mutant integrates with RSpec, Minitest, and Test::Unit.
CI workflow: Mutant supports incremental mode for running mutation testing in CI.
Ruby support: Mutant supports Ruby versions 3.2, 3.3, 3.4, and 4.0 for runtime, syntax, and mutations.
Rails integration: Mutant supports Rails applications with parallel-worker database isolation for PostgreSQL and SQLite.
Rails versions: The Rails integration is verified for Rails 7.2, 8.0, and 8.1.
Subject limitation: Mutant cannot emit mutations for methods defined within closures such as module_eval, class_eval, define_method, or define_singleton_method.
Execution model: Mutant runs exclusively on developers’ machines or in CI.
Source-code privacy: Schirp DSO LTD states that it does not get access to customers’ source code, customer data, or other sensitive material.
Data sharing: Customer information is never shared or sold to anyone.
Support channels: Mutant provides Discord, GitHub Issues, and release announcements as communication channels.
Commercial licensing: Commercial subscriptions are required per developer using Mutant on commercial code, while CI execution requires no additional subscriptions.
Creator: Mutant was created and is developed by Markus Schirp and is cited as subject of IEEE-published research.
Headquarters: Naxxar, Malta
Price from: $20.83/mo

Where it ranks on Freedom251

Best Mutation Testing Tools in 2026#2 of 25

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Sources

github.com/mbj/mutant· checked 1 Oct 2026
github.com/mbj/mutant/blob/main/docs/limitations.m· checked 1 Oct 2026
github.com/mbj/mutant/blob/main/docs/commercial.md· checked 1 Oct 2026