Mocking es modules in browser mode

[alexprudhomme]

Describe the bug

Is module mocking properly implemented in browser mode ? I can't seem to make it work. I saw this PR and supposedly it is suppose to work.
I am mocking my package like so :

vi.mock('uuid', () => ({
  v4: 'mocked-id',
}));

What am I doing wrong ? I added a stackblitz for a more complete example.

Thanks

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-mzcobmhk?file=test%2Fbasic.test.ts

System Info

System:
    OS: macOS 15.2
    CPU: (12) arm64 Apple M3 Pro
    Memory: 1.83 GB / 36.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.12.0 - ~/.nvm/versions/node/v22.12.0/bin/node
    npm: 11.0.0 - ~/.nvm/versions/node/v22.12.0/bin/npm
  Browsers:
    Chrome: 131.0.6778.265
    Safari: 18.2
  npmPackages:
    vite: 5.4.11 => 5.4.11

Used Package Manager

npm

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[hi-ogawa]

Your stackblitz is working after downloading locally. It's possible that browser mode might break on stackblitz.

Can you provide more details if it breaks on your local?

[github-actions]

Hello @alexprudhomme. Please provide a minimal reproduction using a GitHub repository or StackBlitz (you can also use examples). Issues marked with needs reproduction will be closed if they have no activity within 3 days.