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Stryker Mutator
What it is
Stryker Mutator performs mutation testing to assess how well unit tests detect changes in code. It inserts mutations into source code and runs tests against the altered version. It supports JavaScript and TypeScript, C#, and Scala, with more than 30 mutation types. The project is test-runner agnostic; documented integrations include Cucumber, Jasmine, Jest, and Karma, among other listed runners. Code analysis and parallel test processes are intended to speed up runs. The FAQ notes that mutation runs can be slow and recommends improving unit-test performance or limiting 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 and is 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 a mutation score alone.
For and against
For
- Supports JavaScript, TypeScript, C#, and Scala
- Includes more than 30 mutations
- Parallel execution helps speed up testing
- Free under the Apache 2.0 license
Against
- Mutation runs can be slow
- Dashboard backend currently supports github.com only
- Dashboard setup uses a GitHub account
The verdict
Stryker Mutator provides mutation testing across several languages and works with a range of test runners. Its cloud dashboard is useful for open-source reporting, though its Git provider support is currently limited to github.com.
Who it suits
Stryker may suit developers and teams working in JavaScript or TypeScript, C#, or Scala who want to assess unit-test effectiveness. Its dashboard can suit open-source projects that want hosted reports or score badges.
Plans and prices
Stryker Mutator
Open source mutation testing for JavaScript/TypeScript, C# and Scala · Apache 2.0 license
Read 30 Sep 2026 · stryker-mutator.io
On the record
- 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 · read 30 Sep 2026
- Dashboard integration
- The dashboard setup uses a GitHub account and enables reporting for a repository.stryker-mutator.io · read 30 Sep 2026
- Dashboard provider limit
- The dashboard documentation says its backend currently supports github.com as a Git provider.stryker-mutator.io · read 30 Sep 2026
- License
- Stryker is released under the Apache 2.0 license.stryker-mutator.io · read 30 Sep 2026
- Mutations
- The product site says Stryker supports more than 30 mutations.stryker-mutator.io · read 30 Sep 2026
- Performance
- Stryker uses code analysis and parallel test runner processes to speed up mutation testing.stryker-mutator.io · read 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.stryker-mutator.io · read 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.stryker-mutator.io · read 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.stryker-mutator.io · read 30 Sep 2026
- Security
- Stryker says it mutates only source code to avoid false positives.stryker-mutator.io · read 30 Sep 2026
- Setup
- Stryker.NET is installed using NuGet, while the Stryker4s guide provides sbt, Mill, and Maven plugin setup paths.stryker-mutator.io · read 30 Sep 2026
- Support
- The documentation directs users to Slack for help and bug discussions, with bug reporting guidance also available.stryker-mutator.io · read 30 Sep 2026
- Supported languages
- Stryker supports JavaScript and TypeScript, C#, and Scala.stryker-mutator.io · read 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.stryker-mutator.io · read 30 Sep 2026
