Stryker Mutator

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Score6.7

Rank#5 of 25

PriceFree

Free planYes

Runs onAPI, Self-hosted

Summary

Stryker Mutator assesses how well unit tests catch code changes by introducing mutations and running the tests against the altered code. It supports JavaScript and TypeScript, C#, and Scala, with more than 30 mutations. The project is test runner agnostic; listed runner options include Cucumber, Jasmine, Jest, Karma, Mocha, Tap, Vitest, and a command runner. Code analysis and parallel execution are intended to speed up runs, though the FAQ notes that mutation runs can be slow and suggests improving unit-test performance or restricting the files tested. Stryker says it changes only source code to avoid false positives. The project is free and released under the Apache 2.0 license. Its cloud dashboard hosts reports and mutation score badges, free for open source. Dashboard setup uses a GitHub account, and the backend currently supports github.com as a Git provider. Reports can be sent from Stryker or by HTTP PUT with an API key, as a full report or mutation score only.

Who it is for

Stryker suits developers working in JavaScript, TypeScript, C#, or Scala who want to assess unit-test effectiveness. Its dashboard may suit open-source projects that want hosted reports or score badges.

What is good

Supports JavaScript, TypeScript, C#, and Scala.
More than 30 mutations are supported.
Parallel execution and incremental analysis are available.
Dashboard is free for open source.
Apache 2.0 license.

What to know first

Mutation runs can be slow.
Dashboard backend currently supports github.com only.
Dashboard setup uses a GitHub account.

Verdict

Stryker offers mutation testing across four language groups and supports a range of test runners. Allow for potentially slow runs, and note the GitHub provider limit if you plan to use its dashboard.

Stryker Mutator plans and pricing

All plans

Stryker Mutator Free Open source mutation testing for JavaScript/TypeScript, C# and Scala · Apache 2.0 license stryker-mutator.io · 30 Sept 2026

Compared on mutation testing tools

Free plan: Yesstryker-mutator.io
Supported languages: JavaScript, TypeScript, C#, Scalastryker-mutator.io
Test frameworks: Cucumber, Jasmine, Jest, Karma, Mocha, Tap, Vitest, command runnerstryker-mutator.io
Incremental analysis: Yesstryker-mutator.io
Parallel execution: Yesstryker-mutator.io
Surviving mutant reports: Yesstryker-mutator.io
Mutation quality gate: Yesstryker-mutator.io
Mutation operators: Arithmetic Operator, Array Declaration, Block Statement, Boolean Literal, Conditional Expression, Equality Operator, Logical Operator, Method Expression, Object Literal, Optional Chaining, Regex, String Literal, Unary Operator, Update Operatorstryker-mutator.io

Facts

Purpose: Stryker performs mutation testing by inserting changes into code and running unit tests against the changed code to assess test effectiveness.stryker-mutator.io · 30 Sept 2026
Mutations: The product site says Stryker supports more than 30 mutations.stryker-mutator.io · 30 Sept 2026
Performance: Stryker uses code analysis and parallel test runner processes to speed up mutation testing.stryker-mutator.io · 30 Sept 2026
Test runners: Stryker is described as test runner agnostic, and StrykerJS documentation lists plugins for test runners including Cucumber, Jasmine, Jest, and Karma.stryker-mutator.io · 30 Sept 2026
Dashboard: The open source dashboard hosts mutation testing reports in the cloud and provides mutation score badges; it is free to use for open source.stryker-mutator.io · 30 Sept 2026
Dashboard integration: The dashboard setup uses a GitHub account and enables reporting for a repository.stryker-mutator.io · 30 Sept 2026
Report API: Reports can be sent directly from Stryker or by HTTP PUT with an API key, and reports can contain a full report or mutation score only.stryker-mutator.io · 30 Sept 2026
Security: Stryker says it mutates only source code to avoid false positives.stryker-mutator.io · 30 Sept 2026
License: Stryker is released under the Apache 2.0 license.stryker-mutator.io · 30 Sept 2026
Setup: Stryker.NET is installed using NuGet, while the Stryker4s guide provides sbt, Mill, and Maven plugin setup paths.stryker-mutator.io · 30 Sept 2026
Support: The documentation directs users to Slack for help and bug discussions, with bug reporting guidance also available.stryker-mutator.io · 30 Sept 2026
Runtime consideration: Stryker’s FAQ notes that mutation runs can be slow and recommends improving unit test performance and restricting mutations to needed files.stryker-mutator.io · 30 Sept 2026
Dashboard provider limit: The dashboard documentation says its backend currently supports github.com as a Git provider.stryker-mutator.io · 30 Sept 2026