Stryker Mutator
stryker-mutator.io
What it is
Stryker Mutator is mutation-testing software for JavaScript, TypeScript, C#, and Scala. It changes source code in more than 30 defined ways, then runs unit tests against those variants to show how effectively the tests detect faults. The project supports incremental analysis, parallel execution, surviving-mutant reports, and mutation quality gates. It is test-runner agnostic, with listed integrations including Cucumber, Jasmine, Jest, Karma, Mocha, Tap, Vitest, and a command runner. Code analysis and parallel test-runner processes are used to speed runs, although the FAQ notes that mutation jobs can be slow and recommends improving unit-test performance or limiting files. Stryker is free, released under Apache 2.0, and available through API or self-hosted use. Its cloud dashboard stores reports and mutation-score badges, free for open source, with GitHub account setup and github.com as the supported Git provider. Reports can be sent directly or by HTTP PUT with an API key.
Spec sheet
- Purpose
- Stryker performs mutation testing by inserting changes into code and running unit tests against the changed code to assess test effectiveness.Read 30 Sep 2026 · stryker-mutator.io
- Security
- Stryker says it mutates only source code to avoid false positives.Read 30 Sep 2026 · stryker-mutator.io
- Support
- The documentation directs users to Slack for help and bug discussions, with bug reporting guidance also available.Read 30 Sep 2026 · stryker-mutator.io
- License
- Stryker is released under the Apache 2.0 license.Read 30 Sep 2026 · stryker-mutator.io
- 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.Read 30 Sep 2026 · stryker-mutator.io
- Dashboard integration
- The dashboard setup uses a GitHub account and enables reporting for a repository.Read 30 Sep 2026 · stryker-mutator.io
- Dashboard provider limit
- The dashboard documentation says its backend currently supports github.com as a Git provider.Read 30 Sep 2026 · stryker-mutator.io
- Mutations
- The product site says Stryker supports more than 30 mutations.Read 30 Sep 2026 · stryker-mutator.io
- Performance
- Stryker uses code analysis and parallel test runner processes to speed up mutation testing.Read 30 Sep 2026 · stryker-mutator.io
- 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.Read 30 Sep 2026 · stryker-mutator.io
- Runtime consideration
- Stryker’s FAQ notes that mutation runs can be slow and recommends improving unit test performance and restricting mutations to needed files.Read 30 Sep 2026 · stryker-mutator.io
- Setup
- Stryker.NET is installed using NuGet, while the Stryker4s guide provides sbt, Mill, and Maven plugin setup paths.Read 30 Sep 2026 · stryker-mutator.io
- Supported languages
- Stryker supports JavaScript and TypeScript, C#, and Scala.Read 30 Sep 2026 · stryker-mutator.io
- Test runners
- Stryker is described as test runner agnostic, and StrykerJS documentation lists plugins for test runners including Cucumber, Jasmine, Jest, and Karma.Read 30 Sep 2026 · stryker-mutator.io
Plans and prices
Stryker Mutator Free Open source mutation testing for JavaScript/TypeScript, C# and Scala · Apache 2.0 license Read 30 Sep 2026 · stryker-mutator.io
Strong points and limits
Strong points
- Supports JavaScript, TypeScript, C#, and Scala
- More than 30 mutation types
- Parallel execution and incremental analysis
- Free under Apache 2.0 license
- Reports and mutation quality gates
Limits
- Mutation runs can be slow
- Dashboard backend supports github.com only
- Dashboard setup requires a GitHub account
Who it suits
Stryker suits development teams using JavaScript, TypeScript, C#, or Scala who want to measure unit-test effectiveness. It also fits projects needing mutation reports, quality gates, and integrations with several test runners.
Verdict
Stryker Mutator combines broad language and test-runner support with detailed mutation reporting at no software cost. Teams should plan for potentially slow runs and the dashboard’s GitHub-only provider support.
Where Specifiction places it
- Mutation Testing Tools#18 of 257.2
