Coverage

Vitest's coverage works with both engines. Install the provider at the same version as vitest and turn it on as usual:

npm i -D @vitest/coverage-v8
npx vitest run --coverage

What is covered

Coverage reports the files your tests load from your own project, mapped back to their source lines:

• Files Vite loads. These are your tests and most app source. They work as they do in any Vitest project.
• Files Node compiles (native engine). Under engine: 'native', Node loads workspace packages written for React Native (see How It Works). Babel compiles these files for Node. While coverage is on, it also writes a source map for each, so their coverage is reported against your .ts/.tsx lines like everything else.

With provider: 'v8' (Vitest's default), the plugin swaps in a coverage provider that knows about the files Node compiles. That provider is @vitest/coverage-v8 with one change: for those files it reads the code Node ran from the engine's transform cache, instead of asking Vite. The report still says "Coverage report from v8". Your include, exclude, reporters and thresholds apply as before.

What is excluded

• node_modules. This includes React Native itself, and packages that publish Flow, JSX or TypeScript source. @vitest/coverage-v8 skips these, just as Jest's default coveragePathIgnorePatterns does.
• Files outside the project root. In a monorepo, a workspace package that lives next to your app rather than inside it is left out by default. To report it, set coverage.allowExternal: true and add it to coverage.include with a glob relative to the project root, for example include: ['src/**', '../packages/*/src/**'].

Running one project with --project

With --project <name>, Vitest matches coverage.include against that project's root, not the root config's directory. Repo-relative patterns then match nothing, and the report comes out 0/0. For a package beside the project, use a pattern relative to the project, and allow external files:

vitest run --coverage --project app --coverage.include='../lib/src/**' --coverage.allowExternal

Known differences

• In a file Node compiles, import and export lines count as statements, because Babel turns them into require calls and exports assignments. Vite-loaded files do not count those lines. Every other line gets the same verdict either way.
• App source (not a workspace package) that a test loads through Node's require(), for example with jest.requireActual, is still mapped through Vite's output. Its counts can be wrong. Import it instead where you can.
• provider: 'istanbul' instruments files in Vite's transform. It does not see files Node compiles, so use v8 under the native engine.