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Thoroughly test your billing implementation using FunnelFox’s sandbox environment and test cards. Simulate every scenario your customers might encounter without processing real payments.
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

FunnelFox Billing provides a complete sandbox for testing:
1

Funnels preview

Use test cards work in preview mode only.
2

Sandbox indicators

Look for Sandbox badges in the dashboard Subscriptions page when using test credentials. This confirms your sandbox transactions.

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Test cards

Test cards you use depend on the PSP processing your transactions.

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Successful payment cards

Use these cards to simulate successful transactions:
  • Stripe
  • Adyen
  • Checkout.com
  • Other
  • Number: 4242 4242 4242 4242
  • Expiry date: Any valid future date (e.g., 12/34)
  • CVC: Any three-digit CVC
Find more Stripe test cards for successful payment.

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Declined payment cards

Test failure scenarios with these cards:
  • Stripe
  • Adyen
  • Checkout.com
  • Other
  • Number: 4000 0000 0000 0002
  • Expiry date: Any valid future date (e.g., 12/34)
  • CVC: Any three-digit CVC
Find more Stripe test cards for declined payment.

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3D Secure testing

Test Strong Customer Authentication (SCA) flows:
  • Stripe
  • Adyen
  • Checkout.com
  • Other
  • Number: 4000 0027 6000 3184
  • Expiry date: Any valid future date (e.g., 12/34)
  • CVC: Any three-digit CVC
Find more Stripe test cards for 3D Secure.
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

Test the complete subscription journey:
  • Trial to Paid
  • Renewal
  • Failed Payment
  1. Create product with 7-day trial.
  2. Purchase with test card.
  3. Verify trial status in dashboard.
  4. Simulate trial.
  5. Confirm conversion to paid.

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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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Next steps

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