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Stryker Mutator

Stryker Mutator assesses how well unit tests catch code changes by introducing mutations and running the tests against the altered code.

Place
#13 of 25
Score
5.8
Stryker Mutator's website

What Stryker Mutator is

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.

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.

Watch out

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

Who it suits

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.

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.

Plans and prices

From Stryker Mutator's own pricing page, checked 30 Sep 2026.

All about pricing
PlanPriceWhat it gives you
Stryker MutatorFreeOpen source mutation testing for JavaScript/TypeScript, C# and Scala · Apache 2.0 license

The facts

Each one read from Stryker Mutator's own pages, with the date it was checked.

What it does

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.checked 30 Sep 2026
Dashboard integration
The dashboard setup uses a GitHub account and enables reporting for a repository.checked 30 Sep 2026
Dashboard provider limit
The dashboard documentation says its backend currently supports github.com as a Git provider.checked 30 Sep 2026
License
Stryker is released under the Apache 2.0 license.checked 30 Sep 2026
Mutations
The product site says Stryker supports more than 30 mutations.checked 30 Sep 2026
Performance
Stryker uses code analysis and parallel test runner processes to speed up mutation testing.checked 30 Sep 2026
Purpose
Stryker performs mutation testing by inserting changes into code and running unit tests against the changed code to assess test effectiveness.checked 30 Sep 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.checked 30 Sep 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.checked 30 Sep 2026
Security
Stryker says it mutates only source code to avoid false positives.checked 30 Sep 2026
Setup
Stryker.NET is installed using NuGet, while the Stryker4s guide provides sbt, Mill, and Maven plugin setup paths.checked 30 Sep 2026
Support
The documentation directs users to Slack for help and bug discussions, with bug reporting guidance also available.checked 30 Sep 2026
Supported languages
Stryker supports JavaScript and TypeScript, C#, and Scala.checked 30 Sep 2026
Test runners
Stryker is described as test runner agnostic, and StrykerJS documentation lists plugins for test runners including Cucumber, Jasmine, Jest, and Karma.checked 30 Sep 2026

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