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Vitest Runner

Since v7.0

A plugin to use the vitest test runner in Stryker.

Install​

Install @stryker-mutator/vitest-runner locally within your project folder, like so:

npm i --save-dev @stryker-mutator/vitest-runner

Bring your own test runner​

This plugin does not come packaged with it's own version of vitest, instead install your own version of vitest in your project. See @stryker-mutator/vitest-runner's package.json file to discover the minimal required version of vitest.

Configuring​

You can configure the @stryker-mutator/vitest-runner using the stryker.config.json (or stryker.config.js) config file.

{
  "testRunner": "vitest",
  "vitest": {
    "configFile": "vitest.config.js",
    "dir": "packages",
    "related": true
  }
}

vitest.configFile [string | undefined]​

Default: undefined

Specify a 'vitest.config.js' file to be loaded. By default vitest will look for a vitest.config.js (or .ts) file in the root of your project.

vitest.dir [string | undefined]​

Since v7.1

Default: undefined

Configure the --dir <path> command line option. See https://vitest.dev/guide/cli.html#options.

vitest.related [boolean]​

Default: true

If set to true, Vitest will only run tests that are related to the mutated files. It uses the related under the hood. Disable this if your test files don't import your source files directly, for example when using API calls to call your server code in integration tests.

Non overridable options​

The following options will be set by Stryker and cannot be overridden:

{
  threads: true,
  coverage: { enabled: false },
  singleThread: true,
  watch: false,
  bail: options.disableBail ? 0 : 1,
  onConsoleLog: () => false,
}

As you can see, the vitest runner:

  • Will run your tests in a single thread
    This is done because StrykerJS uses it's own parallel workers.
  • Will bail on the first test failure (unless you set disableBail to true).
    This is done to boost performance.
  • Will disable code coverage reporting
    This is done because StrykerJS uses it's own coverage analysis, which is supported.

In-source testing​

Vitest's in-source testing is supported. However, since your tests are in the same file as your code-under-test, you will need to make sure to exclude your tests from being mutated.

For example, you can add the Stryker disable comment (// Stryker disable all) right before if (import.meta.vitest) like so:

 export function add(...args: number[]) {
   return args.reduce((a, b) => a + b, 0)
 }
 
 
 // in-source test suites
+// Stryker disable all: Unit tests start here
 if (import.meta.vitest) {
   const { it, expect } = import.meta.vitest
   it('add', () => {
     expect(add(1, 2, 3)).toBe(6)
   })
 }

Limitations​

The vitest runner has the following limitations:

  • Currently, only threads: true is supported. If you need it if off, please let us know by opening a feature request.
  • Currently, Browser Mode is not supported. If you're using browser mode and want support for it in StrykerJS, please open a feature request
  • Your coverageAnalysis property is ignored. The vitest runner plugin will always use "perTest" coverage analysis (which yields the best performance anyway).