Automatic expect tracking for concurrent tests

Automatic expect tracking for concurrent tests

It's cumbersome and error prone to accept expect for each concurrent test
Automatic tracking is also allows to make tests faster by using .concurrent wrapper, without code modifications

import { describe, it } from 'vitest'

// All tests within this suite will be run in parallel
describe.concurrent('suite', () => {
  it('concurrent test 1', async ({ expect }) => { /* ... */ })
  it('concurrent test 2', async ({ expect }) => { /* ... */ })
  it.concurrent('concurrent test 3', async ({ expect }) => { /* ... */ })
})

Suggested solution

We can add opt in option to use AsyncLocalStorage for node.

import { AsyncLocalStorage } from 'node:async_hooks';

const expectStorage = new AsyncLocalStorage();

const getTestExpect = () => expectStorage.getStore()

const expect = (...args: Parameters<typeof originalExpect>) => {
  const localExpect = getTestExpect()
  if (localExpect) {
    return localExpect(...args)
  }
  return originalExpect(...args)
}
const it = (testFunction: Parameters<typeof originalIt>) => {
    originalIt((...args) => {
      const {expect} = args[0]
      
      expectStorage(expect, testFunction, ...args)
    })
}

Alternative

Zone.js can be also used for async context tracking, since it monkeypatches a lot of stuff - it less reliable

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start by tracing Vitest's existing expect handling and concurrent test execution, then evaluate the proposed opt-in AsyncLocalStorage approach for Node.js. Done should provide automatic per-test expect tracking for concurrent suites without requiring each test to accept expect, with coverage for the described concurrent cases.