coverage.md

title
Coverage | Guide

Coverage

Vitest supports Native code coverage via c8 and instrumented code coverage via istanbul.

Coverage Providers

:::tip Since Vitest v0.22.0 :::

Both c8 and istanbul support are optional. By default, c8 will be used.

You can select the coverage tool by setting test.coverage.provider to either c8 or istanbul:

// vite.config.ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    coverage: {
      provider: 'istanbul' // or 'c8'
    },
  },
})

When you start the Vitest process, it will prompt you to install the corresponding support package automatically.

Or if you prefer to install them manually:

# For c8
npm i -D @vitest/coverage-c8

# For istanbul
npm i -D @vitest/coverage-istanbul

Coverage Setup

To test with coverage enabled, you can pass the --coverage flag in CLI.

{
  "scripts": {
    "test": "vitest",
    "coverage": "vitest run --coverage"
  }
}

To configure it, set test.coverage options in your config file:

// vite.config.ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    coverage: {
      reporter: ['text', 'json', 'html'],
    },
  },
})

Custom Coverage Provider

It's also possible to provide your custom coverage provider by passing 'custom' in test.coverage.provider:

// vite.config.ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    coverage: {
      provider: 'custom',
      customProviderModule: 'my-custom-coverage-provider'
    },
  },
})

The custom providers require a customProviderModule option which is a module name or path where to load the CoverageProviderModule from. It must export an object that implements CoverageProviderModule as default export:

// my-custom-coverage-provider.ts
import type { CoverageProvider, CoverageProviderModule, ResolvedCoverageOptions, Vitest } from 'vitest'

const CustomCoverageProviderModule: CoverageProviderModule = {
  getProvider(): CoverageProvider {
    return new CustomCoverageProvider()
  },

  // Implements rest of the CoverageProviderModule ...
}

class CustomCoverageProvider implements CoverageProvider {
  name = 'custom-coverage-provider'
  options!: ResolvedCoverageOptions

  initialize(ctx: Vitest) {
    this.options = ctx.config.coverage
  }

  // Implements rest of the CoverageProvider ...
}

export default CustomCoverageProviderModule

Please refer to the type definition for more details.

Changing the default coverage folder location

When running a coverage report, a coverage folder is created in the root directory of your project. If you want to move it to a different directory, use the test.coverage.reportsDirectory property in the vite.config.js file.

import { defineConfig } from 'vite'

export default defineConfig({
  test: {
    coverage: {
      reportsDirectory: './tests/unit/coverage'
    }
  }
})

Ignoring code

Both coverage providers have their own ways how to ignore code from coverage reports:

• c8
• ìstanbul

When using TypeScript the source codes are transpiled using esbuild, which strips all comments from the source codes (esbuild#516). Comments which are considered as legal comments are preserved.

For istanbul provider you can include a @preserve keyword in the ignore hint. Beware that these ignore hints may now be included in final production build as well.

-/* istanbul ignore if */
+/* istanbul ignore if -- @preserve */
if (condition) {

For c8 this does not cause any issues. You can use c8 ignore comments with Typescript as usual:

/* c8 ignore next 3 */
if (condition) {