Regression (0.33.0 -> 0.34.0) tests completely break when using jsdom or happy-dom with SvelteKit

[LorenzoBloedow]

Describe the bug

So basically after updating to 0.34.0 from 0.33.0 I get the following error message (redacted):

Error: Failed to load url [REDACTED]/tests/unit/DarkModeSwitch.test.ts (resolved id: [REDACTED]/tests/unit/DarkModeSwitch.test.ts). Does the file exist?

Contrary to what the error message suggests, the file does exist.
I believe this is due to #3491 as it does work when using node instead of jsdom or happy-dom, suggesting the use of the web transform mode instead of ssr is what's causing this.

Note: 0.34.1 doesn't fix the issue.

Reproduction

Open the following StackBlitz and run npm run test
https://stackblitz.com/edit/sveltejs-kit-template-default-fwbgpv

System Info

System:
  OS: Linux 5.0 undefined
  CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  Memory: 0 Bytes / 0 Bytes
  Shell: 1.0 - /bin/jsh
Binaries:
  Node: 16.20.0 - /usr/local/bin/node
  Yarn: 1.22.19 - /usr/local/bin/yarn
  npm: 9.4.2 - /usr/local/bin/npm
  pnpm: 8.6.10 - /usr/local/bin/pnpm
npmPackages:
  vite: ^4.4.2 => 4.4.9 
  vitest: ^0.34.1 => 0.34.1

Used Package Manager

npm

Validations

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[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• sveltejs-kit-template-default-fwbgpv (Open reproduction)

[sheremet-va]

File is outside root. Try disabling server.fs.strict.

[sheremet-va]

File is outside root. Try disabling server.fs.strict.

Indeed the problem is with this. While we are working on fixing this, you can disable strict in test mode or add a tests folder to server.fs.allow

[LorenzoBloedow]

Thank you.
I was under the impression the root directory was where the configuration file lives.

As you suggested, adding the following to vite.config.ts fixes the problem:

server: {
  fs: {
    allow: [".."]
  }
}

[sheremet-va]

I was under the impression the root directory was where the configuration file lives.

Svelte does some magic to fs.allow values, so the root is not included. In the next Vitest version we populate fs.allow ourselves.