[Replacement]: mockdate

[joaopedrodcf]

Package to replace

vitest / node:test / bun:test

Suggested replacement(s)

Depending on the package that the user uses for testing

• vitest ( setSystemTime )
• bun:test ( setSystemTime )
• node:test ( mock.timers )

Manifest type

preferred (lighter or more modern alternative package)

Rationale

mockdate https://npmx.dev/package/mockdate is used to mock dates and so it's useful in tests but for those cases all modern test-runners support mock of dates in a convenient way

https://nodejs.org/en/learn/test-runner/mocking#time

https://vitest.dev/guide/mocking.html#mock-the-current-date

https://bun.com/docs/guides/test/mock-clock

Availability

// node:test with mock.timers since 20.4.0
https://nodejs.org/en/blog/release/v20.4.0

import { test } from 'node:test'
import assert from 'node:assert'

test('freeze date', (t) => {
  t.mock.timers.enable({ apis: ['Date'], now: new Date('2026-01-01') })

  assert.strictEqual(
    new Date().toISOString(),
    '2026-01-01T00:00:00.000Z'
  )
})

vitest

import { vi, test, expect } from 'vitest'

test('freeze date', () => {
  vi.useFakeTimers()
  vi.setSystemTime(new Date('2026-01-01'))

  expect(new Date().toISOString())
    .toBe('2026-01-01T00:00:00.000Z')
})

bun:test

import { test, expect, mock } from "bun:test";

test("freeze time", () => {
  mock.timers.enable({ now: new Date("2026-01-01") });

  expect(new Date().toISOString())
    .toBe("2026-01-01T00:00:00.000Z");
});

Code example (optional)

[43081j]

what version of node introduced those mock timers? would be good to know for if we do add this.

overall seems to make sense to me though since all modern test runners build this in.

[joaopedrodcf]

node introduced mock timers in 20.4.0

https://nodejs.org/en/blog/release/v20.4.0

for vitest and bun both were introduced before the first release 🙏

Also updated the main post