Test the exact endpoint and configuration your public listing advertises: inspect its unpaid payment requirements, make a valid paid request, verify the protected response and settlement evidence, then confirm missing and invalid payments are rejected. Repeat with the listing’s actual protocol version, scheme, network, and verification and settlement path; a passing unit test alone does not prove the deployed listing works.
What an end-to-end x402 test needs to prove
x402 is an HTTP payment protocol for accessing resources such as APIs. In the v2 flow, a client requests a resource, the server returns payment requirements, and the client submits a payment payload with a subsequent request. The server verifies payment either locally or through a facilitator; if valid, it fulfills the request and settles directly or through a facilitator. The response can include payment information. If verification fails, the server can return payment-required information again. See the x402 Foundation repository and v2 specification.
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That flow gives you five observable checks: the public route and unpaid response, the advertised requirements, a successful paid request, rejection of missing or invalid payment, and evidence that the configured settlement path completed. Your test must follow the version and architecture actually advertised and deployed; x402 implementations can differ in protocol version, scheme, network, and settlement design.
Record the listing’s actual configuration first
Before sending requests, capture the listing’s public URL and method, protocol version, scheme, network, amount, recipient, any token details, and whether verification and settlement are local or use a facilitator. Compare these details with what the endpoint returns: the listing description and the live requirements response should agree. The protocol does not identify a universal scheme, network, or facilitator for every listing.
Version matters on the wire. The v2 repository describes the PAYMENT-REQUIRED, PAYMENT-SIGNATURE, and PAYMENT-RESPONSE headers, but older x402 material and implementations can use different conventions. Use the header format for the version the listing claims, rather than copying names from another version.
Run the end-to-end checks
- Request the listed route without payment. Use the exact public URL and HTTP method shown in the listing. Confirm the route is reachable and the response advertises parseable payment requirements rather than returning an unrelated error. Compare the required amount, recipient, scheme, network, and token details, if present, with the listing.
- Send a valid paid request. Use a client compatible with the advertised protocol version, scheme, and network. Have it submit the payment payload as required by that version. Confirm the API returns the protected response body—not merely an accepted request—and inspect any payment-response information the implementation exposes.
- Verify settlement evidence. Follow the implementation’s configured path. If it uses a facilitator, exercise the actual verification and settlement path on its supported scheme and network. If verification or settlement is local, test that local path. Check the outcome evidence your implementation makes available before counting the request as complete; a protected response by itself does not establish that settlement succeeded.
- Try missing and invalid payment. Repeat the request without payment, with malformed payment information, and with payment that does not meet the requirements. Verify that none returns the protected result as a successful paid request. The documented flow allows the server to return payment-required information when verification fails.
- Repeat in the intended environments. During development, test with the selected test network and assets. Separately validate the production network identifiers, provider, recipient, scheme, and facilitator configuration you intend to use. Test-network success does not establish that production configuration works.
Separate code tests from a live listing check
The x402 repository provides a package unit-test command and runnable server and client examples. Use those to check package behavior, but still call the deployed endpoint at the URL shown in the listing. Unit tests do not demonstrate that the public route, listing metadata, deployed configuration, or facilitator integration works together.
Rank #2
For a CLI-based example, Coinbase’s x402 Monetize reference demonstrates checking payment requirements and making a paid request. Treat it as an example client path, not as proof that every listing supports the same client, scheme, or network.
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Keep a reproducible launch record
Record the request URL and method, claimed protocol version, scheme and network, expected and observed requirements, paid-response result, settlement evidence, and outcomes for missing, malformed, and insufficient payment. Include the environment used so a testnet run cannot be mistaken for a production check. This record is a practical way to make the flow repeatable, not an official x402 certification format.
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Rank #3
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