Stryker Mutator

What Stryker Mutator is

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

Who it suits

Stryker suits developers working in its supported languages who want to assess unit-test effectiveness. The dashboard may suit open-source projects using github.com as their Git provider.

Limits

Stryker is free. Its mutation runs can be slow; its FAQ recommends improving unit test performance and restricting mutations to needed files. The dashboard backend currently supports github.com as a Git provider.

Getting started

1. Visit https://stryker-mutator.io/ and choose the setup path for your language.
2. Install Stryker.NET with NuGet, or use the Stryker4s setup guide for sbt, Mill or Maven.
3. Select a supported test runner for your project.
4. Use the available options for incremental analysis, parallel execution and mutation quality gates.
5. For dashboard reporting, connect a GitHub account and enable reporting for a repository.
6. Send reports directly from Stryker or by HTTP PUT with an API key.

Verdict

Stryker provides mutation testing across several languages, with runner options and a report dashboard. Account for potentially slow runs and the dashboard’s stated Git-provider limit.