Thoroughly test your billing implementation using FunnelFox’s sandbox environment and test cards. Simulate every scenario your customers might encounter without processing real payments.
Important: Only test cards work in sandbox mode. Using real card numbers will return an error. This protects you from accidental charges during development.

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Test Environment Setup

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Sandbox Mode

FunnelFox Billing provides a complete sandbox for testing:
1

Use test credentials

Always use test/sandbox API keys from your PSP when developing. Never use production keys until ready to go live.
2

Test mode indicators

Look for “TEST MODE” badges in the dashboard when using test credentials. This confirms you’re in sandbox.
3

Preview vs Published

Test cards work in both preview and published funnels when using test credentials. No difference in behavior.
Sandbox data: Test transactions appear in your dashboard marked as test data. They’re automatically separated from production data and can be filtered or hidden.

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Test Cards Reference

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Successful Payment Cards

Use these cards to simulate successful transactions:
Visa
  • Number: 4242 4242 4242 4242
  • Use any future expiry date
  • Use any 3-digit CVC
  • Use any billing ZIP
Mastercard
  • Number: 5555 5555 5555 4444
  • Same rules for expiry, CVC, ZIP

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Declined Payment Cards

Test failure scenarios with these cards:
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Generic Decline
test-card
Visa: 4000 0000 0000 9995 Mastercard: 5200 0000 0000 1005Simulates a generic card decline without specific reason.
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Insufficient Funds
test-card
Card: 4000 0000 0000 9995Simulates insufficient funds decline. Useful for testing retry logic.
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Lost Card
test-card
Card: 4000 0000 0000 9987Simulates a reported lost card. Should not be retried.
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Expired Card
test-card
Card: 4000 0000 0000 0069Simulates an expired card error. Tests update payment flow.

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3D Secure Testing

Test Strong Customer Authentication (SCA) flows:
1

Required Authentication

Card: 4000 0025 0000 3155Always requires 3D Secure authentication. Customer must complete additional verification.
2

Optional Authentication

Card: 4000 0027 6000 3184Authentication recommended but not required. Tests soft decline handling.
3

Authentication Codes

When prompted for 3D Secure verification:
  • Enter 1234 for successful authentication
  • Enter 1111 or 2222 for failed authentication
  • Enter 3333 for unknown response
  • Enter 4444 for successful with delay
3D Secure flows: These may open additional windows or iframes. Ensure your funnel handles these popups correctly and doesn’t block them.

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Testing Scenarios

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Subscription Lifecycle

Test the complete subscription journey:
  1. Create product with 7-day trial
  2. Purchase with test card
  3. Verify trial status in dashboard
  4. Simulate trial end (contact support)
  5. Confirm conversion to paid

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Edge Cases

Don’t forget to test these scenarios: Payment Method Updates
  • Card expiration during subscription
  • Switching from card to card
  • Invalid card replacement
Subscription Changes
  • Upgrade mid-cycle
  • Downgrade with proration
  • Pause and resume
  • Cancellation and reactivation
International
  • Multi-currency transactions
  • Currency conversion
  • Tax calculations
  • Regional payment methods

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Test Checklist

Before going live, verify these scenarios:

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Payment Processing

  • Successful payment with primary card types
  • Declined payments with various reasons
  • 3D Secure authentication flow
  • International cards and currencies
  • Payment method updates

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Subscription Management

  • Free trial creation and conversion
  • Paid trial processing
  • Subscription renewals
  • Plan upgrades and downgrades
  • Pause and resume functionality
  • Cancellation flow

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Error Handling

  • Network timeouts
  • Invalid card data
  • Duplicate payment prevention
  • Webhook failure recovery
  • PSP outage fallback

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Customer Experience

  • Email notifications
  • Receipt generation
  • Invoice accuracy
  • Refund processing
  • Customer portal access

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Debugging Tips

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Moving to Production

After thorough testing:
1

Switch credentials

Replace test API keys with production credentials in Settings → Integrations
2

Small real transaction

Process a small real payment ($1) to verify everything works
3

Monitor closely

Watch first 10-20 real transactions carefully for any issues
4

Have rollback plan

Keep test environment ready in case you need to revert
Final check: Ensure you’ve removed all test data and debug code before accepting real payments. Double-check webhook URLs point to production endpoints.

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Next Steps

Testing complete? Continue with: