vitest.config.js in 5.1.1 - Unknown Error: [object object]

[kevreth]

Astro Info

$ npx astro info
Astro                    v5.1.1
Node                     v22.8.0
System                   Linux (x64)
Package Manager          npm
Output                   static
Adapter                  none
Integrations             @astrojs/vue

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

This is a continuation of #12384, which is closed but the issue remains. Running any vitest, with Astro involved or not, with the recommended vitest.config.ts from the docs yields

Unhandled Error Unknown Error: [object Object]

What's the expected result?

Tests pass. As it is, executing in the termainal of the MRE

npx vitest test/basic.test.ts

Causes that test, and all tests if any are added, to fail.

Link to Minimal Reproducible Example

https://stackblitz.com/github/withastro/astro/tree/latest/examples/with-vitest?file=package.json

Participation

• I am willing to submit a pull request for this issue.

[kevreth]

Downgrading to Astro 4.16.17 immediately resolves the problem.

[ascorbic]

This is an upstream problem with Vitest support for Vite 6. You can install the beta version of vitest, which should work: try [email protected]. You can follow progress and see other possible workarounds at #12662