عرض عملي: مطاردة اختبار متقلّب

خطوة بخطوة

1. Run the suite ten times and note which test fails sometimes.
2. Run that test alone, then in random order, to see whether it depends on order.
3. Spot the cause: it uses LocalDate.now() near midnight, or leftover data.
4. Inject a fixed Clock and use unique data.
5. Planned mistake: add Thread.sleep and see it still flake; replace with a deterministic clock.
6. Run ten times again and record the runtime.