Payment Integration Testing Checklist

Payment bugs cost you money and customer trust. AI-generated payment integrations frequently have webhook handling errors, incorrect amount calculations, and broken error recovery. This checklist ensures your payment flow works correctly before you start accepting real transactions.

Last updated: 2026-03-14

Payment Flow

Successful payment completes the full flow

Process a test payment from start to finish and verify the order is created, the user is notified, and access is granted.

Payment amounts are calculated correctly

Verify that the amount charged matches the displayed price including taxes, shipping, and discounts.

Currency is displayed and charged correctly

If supporting multiple currencies, verify amounts display in the correct currency and charges process accurately.

Payment confirmation is shown and emailed

After successful payment, verify both an on-screen confirmation and a receipt email are delivered.

Error Handling

Declined cards show clear error messages

Use test card numbers for declined transactions and verify the app displays a helpful message, not a technical error.

Insufficient funds are handled gracefully

Simulate an insufficient funds error and verify the user can retry with a different payment method.

Network timeout during payment is handled

Simulate a slow or failed network request during payment and verify the app does not create a partial charge.

3D Secure authentication works correctly

Test with cards that require 3D Secure verification and verify the authentication flow completes without errors.

Duplicate charges are prevented

Submit the payment form multiple times rapidly and verify only one charge is processed.

Webhooks and Backend

Payment webhooks are received and processed

Verify that webhook events from the payment provider trigger the correct backend actions like order fulfillment.

Webhook signature verification is implemented

Check that the backend validates webhook signatures to prevent spoofed payment notifications.

Failed webhooks are retried or logged

Simulate a webhook processing failure and verify the system retries or logs the failure for manual review.

Refund processing works correctly

Process a test refund and verify the amount is returned, the order status updates, and the user is notified.

Subscription Payments

Subscription creation charges the correct amount

Create a new subscription and verify the initial charge matches the plan price.

Plan changes prorate correctly

Upgrade or downgrade a subscription mid-cycle and verify the prorated amount is calculated correctly.

Cancellation stops future charges

Cancel a subscription and verify no further charges are processed after the current period ends.

Failed renewal payment triggers appropriate action

Simulate a failed renewal payment and verify the app handles it with retry logic or account restriction.

Frequently Asked Questions

How do I test payments without charging real money?

Every major payment processor offers a test or sandbox mode. Use Stripe test mode with test card numbers, PayPal sandbox accounts, or equivalent test environments. Never test with real payment methods.

What is the most common payment bug in AI-generated apps?

Missing or incorrect webhook handling is the most common issue. The payment succeeds on the provider side, but the app never receives or processes the confirmation, leaving users without access to what they paid for.

Should I test subscription lifecycle events?

Yes. Test creation, renewal, upgrade, downgrade, cancellation, and failed payment for every subscription plan. Use the payment provider's test clock or event simulation tools to trigger lifecycle events.

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