عرض عملي: محاكاة النتائج الثلاث لبوابة الدفع

خطوة بخطوة

1. Create an in-memory fake OrderRepository.
2. Mock PaymentGateway; stub an approval and assert the order is PAID.
3. Stub a decline and assert the order is PAYMENT_FAILED.
4. Stub thenThrow(new GatewayTimeoutException()) and assert the order stays PENDING.
5. Planned mistake: verify five internal calls; then rename a private method and watch the test break for no good reason. Fix by asserting on results.