Watch Mode Import Succeeds But Reruns Tests with Stale Code with "Incorrect" Import Path

Describe the bug

Hi. In watch mode, if I specify an import in a test assuming a path relative to the project’s root, tests will run correctly the first time, changes to the source module will trigger a rerun, but the imported source module will not reflect any updated code.

Here is a minimal example:

// src/sum.js

export function sum(a, b) {
  return a + b
}

// test/sum.test.js
import { expect, test } from 'vitest'

// note the relative path '.' rather than '..'
import { sum } from './src/sum'

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3)
})

Running vitest will succeed — the import resolves correctly and the test will pass. Without quitting vitest, changes to src/sum.js will (correctly) trigger a retest but the actual code change in src/sum.js will not be reflected in the test. So if we change the function to return a + b + b, the tests will continue to pass until we stop and restart vitest.

Changing the import in test/sum.test.js to

import { sum } from '../src/sum'

eliminates the problem.

It seems like the correct behavior would be for the import using a path rooted at the project root to fail, since, relative to test/sum.test.js, ./src/sum.js doesn’t exist.

Reproduction

Example repo: https://github.com/drocco007/vitest_watch_mode_issue

To reproduce the issue:

• clone the repo
• npm install
• npm run test
• edit src/sum.js, make a change — for example to introduce a bug into the calculation — and save

Expected behavior:

• the tests will rerun
• the tests will reflect the updated code in src/sum.js

Actual behavior:

• the tests will rerun (correct)
• the tests will reflect the code as it existed when npm run test was first executed, not the current state of the file

System Info

$ npx envinfo --system --npmPackages '{vitest,@vitest/*,vite,@vitejs/*}' --binaries --browsers

  System:
    OS: Linux 5.15 Ubuntu 22.04.1 LTS 22.04.1 LTS (Jammy Jellyfish)
    CPU: (8) x64 Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz
    Memory: 9.25 GB / 15.29 GB
    Container: Yes
    Shell: 5.1.16 - /bin/bash
  Binaries:
    Node: 18.17.1 - /usr/bin/node
    npm: 10.0.0 - ~/.npm-global/bin/npm
  Browsers:
    Brave Browser: 108.1.46.144
    Chrome: 108.0.5359.124
    Chromium: 117.0.5938.132
  npmPackages:
    vitest: ^1.3.1 => 1.3.1

### Used Package Manager

npm

### Validations

- [X] Follow our [Code of Conduct](https://github.com/vitest-dev/vitest/blob/main/CODE_OF_CONDUCT.md)
- [X] Read the [Contributing Guidelines](https://github.com/vitest-dev/vitest/blob/main/CONTRIBUTING.md).
- [X] Read the [docs](https://vitest.dev/guide/).
- [X] Check that there isn't [already an issue](https://github.com/vitest-dev/vitest/issues) that reports the same bug to avoid creating a duplicate.
- [X] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/vitest-dev/vitest/discussions) or join our [Discord Chat Server](https://chat.vitest.dev).
- [X] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.

Clone the linked reproduction, run npm install and npm run test, then inspect src/sum.js and test/sum.test.js while editing the source in watch mode. Confirm that the tests rerun and reflect the changed implementation rather than the initial code; the issue does not name a Vitest source file or failing test to begin with.