CVV Test API Documentation: Sandbox CVC Testing Guide

A CVV test API lets you exercise CVC validation inside a payment gateway sandbox. You send a gateway-issued test card number plus a CVC value to a test endpoint, and the gateway returns a simulated result. No real card is charged and no live network authorization occurs. Real card numbers and real CVC values must never be sent to a sandbox or stored on your servers after an authorization attempt.

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Prerequisites

• Sandbox or test-mode API keys from your payment provider
• The provider test card list, which pairs each test card number with expected behaviors
• An HTTP client such as curl, Postman, or your application test suite
• A clear boundary between test credentials and live credentials in your config

What the CVC Field Does in Test Mode

In a live charge, the CVC is passed to the issuer for verification and is never returned to the merchant. In test mode, the gateway simulates that check. Behavior varies by provider. Some sandboxes accept any three-digit value for most test cards and only branch on the card number. Others reserve specific CVC values to trigger a failed CVC check so you can test your decline path. American Express test cards use a four-digit CVC.

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How to Send a Test CVC Request

1. Switch your client to the sandbox base URL and load a test secret key.
2. Build the payment payload with a test card number, an expiration date in the future, and the CVC field named as your provider documents it.
3. Send the request to the sandbox charge, payment intent, or card verification endpoint.
4. Read the CVC result field in the response, which is often separate from the overall status.
5. Log the response code and any decline reason to your test fixtures.
6. Repeat with the provider test card that maps to a CVC failure, then confirm your application shows the correct message.

Common Response Signals

• A success status with a CVC check of pass means the simulated verification matched.
• A CVC check of fail usually returns a decline code such as incorrect_cvc or cvv_failure.
• An unavailable or unchecked result means the provider did not simulate a CVC outcome for that card.
• A 400-level error means your payload shape is wrong, not that the card failed.

Errors Worth Testing

Map every simulated decline to a user-facing state. A CVC mismatch should prompt a retry of that field, not a full re-entry of the card. Rate limit errors and expired test cards should also have fixtures. Keep the sandbox test data in source control so the suite stays reproducible.

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Compliance Notes

PCI DSS treats the CVC as sensitive authentication data. It cannot be stored after authorization, even encrypted, and it cannot appear in logs, receipts, or analytics events. Test values are safe to log because they belong to the provider, not to a cardholder. Route production traffic only to live endpoints and confirm your sandbox keys cannot reach them.

Verification Checklist

1. Confirm the test key is used for every sandbox request.
2. Confirm the CVC field name matches the provider schema.
3. Confirm a passing and a failing CVC case both exist in the suite.
4. Confirm no CVC value is written to persistent storage in production code paths.