Coverage

Vitest supports Native code coverage via v8 and instrumented code coverage via istanbul.

Coverage Providers

TIP

Since Vitest v0.22.0

Both v8 and istanbul support are optional. By default, v8 will be used.

You can select the coverage tool by setting test.coverage.provider to v8 or istanbul:

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

export default defineConfig({
  test: {
    coverage: {
      provider: 'istanbul', // or 'v8'
    },
  },
});

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:

bash

# For v8
npm i -D @vitest/coverage-v8

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

Coverage Setup

To test with coverage enabled, you can pass the --coverage flag in CLI. By default, reporter ['text', 'html', 'clover', 'json'] will be used.

json

{
  "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:

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.

diff

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

For v8 this does not cause any issues. You can use c8 ignore comments with Typescript as usual:

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

Other Options

To see all configurable options for coverage, see the coverage Config Reference.

Vitest UI

Since Vitest 0.31.0, you can check your coverage report in Vitest UI.

Vitest UI will enable coverage report when it is enabled explicitly and the html coverage reporter is present, otherwise it will not be available:

enable coverage.enabled=true in your configuration or run Vitest with --coverage.enabled=true flag
add html to the coverage.reporters list: you can also enable subdir option to put coverage report in a subdirectory