عرض عملي: إصلاح تسرّب بيانات الاختبار

خطوة بخطوة

1. Show two tests that pass alone but one fails when run together.
2. Find the cause: both insert the same email, or one counts all rows.
3. Run in random order (JUnit method order setting) to reproduce.
4. Fix with unique data per test and a cleanup in @BeforeEach.
5. Planned mistake: adding @Transactional to a test that uses real HTTP and seeing the leak remain; explain why and use cleanup instead.
6. Run the suite ten times to confirm.