fix(fakeTimers): force queueMicrotask and nextTick in toNotFake

docs/config/faketimers.md

@@ -32,9 +32,7 @@ Mocking `nextTick` is not supported when running Vitest inside `node:child_proce
 - **Type:** `('setTimeout' | 'clearTimeout' | 'setImmediate' | 'clearImmediate' | 'setInterval' | 'clearInterval' | 'Date' | 'nextTick' | 'hrtime' | 'requestAnimationFrame' | 'cancelAnimationFrame' | 'requestIdleCallback' | 'cancelIdleCallback' | 'performance' | 'queueMicrotask' | 'Intl' | 'Temporal')[]`
 - **Default:** `[]`
 
-An array with names of global methods and APIs to keep native. All other available timers will be mocked. For example, to keep `setInterval()` native and mock all other timers, specify this property as `['setInterval']`.
-
-Mocking `nextTick` is not supported when running Vitest inside `node:child_process` by using `--pool=forks`. When running with `--pool=forks`, Vitest automatically adds `nextTick` to the `toNotFake` array.
+An array of global methods and APIs to exclude from fake timers. Vitest always excludes `nextTick` and `queueMicrotask` when this option is used. To fake either API, use `toFake` instead.
 
 ::: warning
 Using both `toFake` and `toNotFake` together is not supported.

packages/vitest/src/integrations/mock/timers.ts

@@ -169,6 +169,14 @@ export class FakeTimers {
       toFake = (Object.keys(this._fakeTimers.timers) as FakeMethod[])
         .filter(timer => timer !== 'nextTick' && timer !== 'queueMicrotask')
     }
+    else if (toFake === undefined && toNotFake !== undefined) {
+      // Do not mock timers internally used by node via `toNotFake`
+      for (const timer of ['nextTick', 'queueMicrotask'] as const) {
+        if (!toNotFake.includes(timer)) {
+          toNotFake = [...toNotFake, timer]
+        }
+      }
+    }
     if (isChildProcess() && toNotFake && !toNotFake.includes('nextTick')) {
       toNotFake = [...toNotFake, 'nextTick']
     }

test/unit/test/fixtures/timers.suite.ts

@@ -154,7 +154,7 @@ describe('FakeTimers', () => {
       expect(global.clearImmediate).toBe(origClearImmediate)
     })
 
-    it.skipIf(isChildProcess)('mocks process.nextTick when toNotFake does not include nextTick', () => {
+    it.skipIf(isChildProcess)('does not mock process.nextTick when toNotFake is used without nextTick', () => {
       const origNextTick = () => {}
       const global = {
         Date: FakeDate,
@@ -166,7 +166,21 @@ describe('FakeTimers', () => {
       }
       const timers = new FakeTimers({ global, config: { toNotFake: [] } })
       timers.useFakeTimers()
-      expect(global.process.nextTick).not.toBe(origNextTick)
+      expect(global.process.nextTick).toBe(origNextTick)
+    })
+
+    it('does not mock queueMicrotask when toNotFake is used', () => {
+      const origQueueMicrotask = () => {}
+      const global = {
+        Date: FakeDate,
+        clearTimeout,
+        queueMicrotask: origQueueMicrotask,
+        setTimeout,
+      }
+      const timers = new FakeTimers({ global, config: { toNotFake: ['Temporal'] } })
+      timers.useFakeTimers()
+      expect(global.queueMicrotask).toBe(origQueueMicrotask)
+      expect(global.setTimeout).not.toBe(setTimeout)
     })
 
     it.runIf(isChildProcess)('does not mock process.nextTick when toNotFake does not include nextTick and is child_process', () => {