feat: add vitest.config.ts to module starter template for @nuxt/test-utils v4 compatibility

[narr07]

Environment

Operating system	Windows 10.0.26200
CPU	13th Gen Intel(R) Core(TM) i3-1315U (8 cores)
Node.js version	v22.23.1
nuxt/cli version	3.37.0
Package manager	npm@10.9.8
Nuxt version	4.5.1
Nitro version	2.13.4
Builder	vite@8.2.0
Config	-
Modules	-

Reproduction

https://github.com/nuxt/starter/tree/module

Describe the bug

Summary

The module starter template (nuxt/starter#module) does not include a
vitest.config.ts file. With the release of @nuxt/test-utils v4, this
omission causes test failures because the Nuxt vitest environment must now be
explicitly configured via defineVitestConfig or defineVitestProject.

Current behavior

Running npm run test (or vitest) on a freshly scaffolded module project
results in:

Cannot read properties of undefined (reading 'config') at test/basic.test.ts:5:1

This happens because:

1. No vitest.config.ts is present → vitest runs without a nuxt environment
2. @nuxt/test-utils v4 moved Nuxt environment setup from setupFiles to
   beforeAll, so any Nuxt composable or setup() call at the top level of
   a describe block throws before the environment is initialized

Expected behavior

The module starter template should ship with a vitest.config.ts that correctly
configures the test environment for @nuxt/test-utils v4, following the
official testing docs.

Proposed vitest.config.ts

import { defineConfig } from 'vitest/config'
import { defineVitestProject } from '@nuxt/test-utils/config'

export default defineConfig({
  test: {
    projects: [
      {
        test: {
          name: 'unit',
          include: ['test/unit/*.{test,spec}.ts'],
          environment: 'node',
        },
      },
      await defineVitestProject({
        test: {
          name: 'nuxt',
          include: ['test/nuxt/*.{test,spec}.ts'],
          environment: 'nuxt',
          environmentOptions: {
            nuxt: {
              rootDir: './playground',
            },
          },
        },
      }),
    ],
  },
})

Additional context

Additional notes

• package.json should have "type": "module" for ESM compatibility
  with the config file (or the file should be renamed to vitest.config.mts)
• Test files should be reorganized under test/nuxt/ for Nuxt-environment
  tests and test/e2e/ for end-to-end tests using setup() from
  @nuxt/test-utils/e2e
• The existing test/basic.test.ts in the template should be moved to
  test/nuxt/basic.test.ts

Environment

• @nuxt/test-utils: v4.x
• vitest: v4.x
• Template: nuxt/starter#module

References

• @nuxt/test-utils v4.0.0 release notes
• Official testing docs
• Breaking change: environment setup moved to beforeAll
  (#1516)

### Logs

```shell-script

[coderabbitai]

🔗 Related PRs

#1708 - fix(config): nested browser-mode Nuxt Vitest projects with viteEnvironmentApi [merged]
#1720 - build: migrate to tsdown [closed]
#1724 - fix(config): browser setup in defineVitestProject [merged]
#1725 - feat(browser): add render helper for vitest browser mode [open]
#1737 - fix(config): inline config for useRuntimeConfig() composable [merged]
#1763 - fix(config): don't run includeSource in both projects in defineVitestConfig [merged]

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💬 Have feedback or questions? Drop into our discord!

[yamachi4416]

The template's initial test is an E2E test in a Node vitest environment and works out of the box.
(it might be kept minimal by default so developers can customize it as needed)
However, adding tests for a Nuxt vitest environment requires vitest.config.ts following the official docs, as you noted.
To skip manual setup, you can run npx nuxt module add @nuxt/test-utils to set it up using an interactive wizard.