Mocking a module that is a class will have all of its instances to share the same 'mock'

[rafaelmaiolla]

Describe the bug

When using vi.mock('./SomeClass.ts'); to mock a module that is a class exported as default export class SomeClass {...}, it will have all of its instances to share the same 'mock' attribute in the methods.

And if your code create multiple instances of that SomeClass, it is not possible to check if a method was called from one or the other instance as both will share the mock attribute.

This works fine in Jest, both checks above will be false.

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-i4zx4z?file=test%2Fbasic.test.ts

System Info

System:
    OS: Windows 10 10.0.19045
    CPU: (12) x64 Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz   
    Memory: 5.79 GB / 31.91 GB
  Binaries:
    Node: 18.15.0 - ~\.nvm\versions\node\v18.15.0\bin\node.EXE
    npm: 9.5.0 - ~\.nvm\versions\node\v18.15.0\bin\npm.CMD    
  npmPackages:
    @vitejs/plugin-react-swc: 3.4.0 => 3.4.0
    @vitest/coverage-v8: 0.34.6 => 0.34.6
    vite: 4.4.11 => 4.4.11
    vitest: 0.34.6 => 0.34.6

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.