feat: automatically advance fake timers in Vitest

[TrevorBurnham]

This PR adds automatic detection of fake timers from both Jest and Vitest, eliminating the need for users to manually configure advanceTimers when using vi.useFakeTimers() or jest.useFakeTimers().

Fixes #1115

Problem

When using Vitest with fake timers, userEvent would timeout because it wasn't advancing the fake timers. Users had to work around this by shimming the Jest global:

globalThis.jest = {
  advanceTimersByTime: vi.advanceTimersByTime.bind(vi),
}

This happened because userEvent only checked for Jest's timer APIs, not Vitest's.

Solution

Auto-detect Jest and Vitest timer globals so advanceTimers doesn't need to be configured manually.

• New getTimerAdvancer() in src/utils/misc/timerDetection.ts — checks globalThis.jest and globalThis.vi for an advanceTimersByTime method and returns a bound reference to it (or null).
• wait.ts calls getTimerAdvancer() when the user hasn't provided a custom advanceTimers option, falling back to the default no-op if no framework is detected.
• Manual advanceTimers configuration still takes precedence over auto-detection.
• When both Jest and Vitest globals are present, Jest takes precedence for backward compatibility.

Before

test('button click', async () => {
  vi.useFakeTimers()
  globalThis.jest = {
    advanceTimersByTime: vi.advanceTimersByTime.bind(vi),
  }
  const user = userEvent.setup()
  await user.click(button) // Would timeout without workaround
})

After

test('button click', async () => {
  vi.useFakeTimers()
  const user = userEvent.setup()
  await user.click(button) // Works automatically
})

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[JoueBien]

Before this is merged you'll probably want to fix the circular import of defaultAdvanceTimers which shows up in a warning when build is run.

When using this is the intent to have jest in the languageOptions.globals?
like so:

 languageOptions: {
      globals: {
        ...globals.jest,
      },
    },

Or for earlier versions of jest in a set up file:

global.jest = {
  ...jest,
};

[TrevorBurnham]

@JoueBien Thanks! I've updated the PR branch.

[pbomb]

Just wondering if the plan is still to land this fix. We're seeing this in a large monorepo in which we'd like to incrementally migrate from Jest to Vitest.

[TrevorBurnham]

I've rebased the branch. The build failure in CI appears to be unrelated to this change:

error eslint-visitor-keys@5.0.1: The engine "node" is incompatible with this module. Expected version "^20.19.0 || ^22.13.0 || >=24". Got "20.12.2"

[JoueBien]

Looking at that error I'd probably try the following things:

• Running npm install after the rebase to make sure the lock file is up to date.
• That error is may be caused by one of the eslint- packages in the package.json file. If you remove the ^ to fix the version does the error go away?