testland/jest-fake-timers
Wraps Jest's built-in modern fake-timers (built on @sinonjs/fake-timers since Jest 27): jest.useFakeTimers(), jest.setSystemTime(), jest.advanceTimersByTime(), jest.runAllTimers(), and jest.useRealTimers() for selective restoration. Use when testing JS/TS code in Jest where setTimeout / setInterval / Date / Date.now need deterministic control.
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This plugin was archived by the owner on Oct 11, 2026
Reason: Tile archived: Retired from testland/qa (merged into another skill or removed).
advanced-scenarios.mdreferences/
jest fake-timers advanced scenarios
Selective faking, DST/timezone tests, and fake-timer + mocked
fetch interplay extracted from the core skill. Enable / advance
/ run-all usage stays in SKILL.md.
Selective faking
jest.useFakeTimers({
doNotFake: ['nextTick', 'queueMicrotask'],
now: new Date('2026-05-20T14:30:00Z').getTime(),
});DST tests
Set the runtime zone before enabling fake timers, then set system time to the UTC instant of the transition.
beforeAll(() => {
process.env.TZ = 'America/New_York';
jest.useFakeTimers();
});
test('spring-forward behaviour', () => {
jest.setSystemTime(new Date('2026-03-08T06:30:00Z')); // 02:30 EDT - invalid local
expect(new Date().toString()).toMatch(/03:30/); // Browser/Node normalises
});Mix fake-timers with real fetch
If fetch is mocked separately, ensure the mock awaits a faked
timer too:
test('debounce + fetch', async () => {
global.fetch = jest.fn().mockResolvedValue({ json: () => ({ ok: true }) });
myDebouncedFetch();
await jest.advanceTimersByTimeAsync(300);
expect(fetch).toHaveBeenCalled();
});