Explore Tests
Pick a test, point your client at the endpoint, and see exactly what it does. Every test is a link, so you can share one or bookmark it. Testnets only, and nothing is stored.
- Expired MPP challenge
An MPP challenge on Base Sepolia whose WWW-Authenticate expires is in the past.
Your client should Refuse a challenge it cannot satisfy in time.
- Two MPP challenges at once
One WWW-Authenticate carrying two Payment challenges on Base Sepolia, an inflated decoy before the real one.
Your client should Pay the cheaper challenge, not blindly the first.
- MPP legacy network name
An MPP challenge whose request payload names the network base-sepolia rather than eip155:84532.
Your client should Refuse it rather than guess which chain it means.
- MPP undecodable request
An MPP challenge whose base64url request parameter is not decodable at all.
Your client should Fail cleanly, and not crash.
- MPP 402 with no challenge
A bare 402 and a problem+json body, with no WWW-Authenticate header to answer.
Your client should Treat it as unpayable, and not hang.
- MPP mismatched recipient
An MPP challenge on Base Sepolia paying an address the endpoint was not configured with.
Your client should Notice who it is about to pay.
- MPP inflated amount
An MPP challenge whose request payload asks 1000x the price, still atomic-shaped.
Your client should Catch it against its own maximum, or the asset's decimals.
- MPP amount as a number
An MPP request payload whose amount is a bare JSON number instead of an atomic-units string.
Your client should Refuse it, or read the amount as a big-integer string.
- Oversized MPP header
An MPP challenge padded past the 8KB header buffer many proxies and hardened clients enforce.
Your client should Fail cleanly; a reduced-limit HTTP parser rejects the response.
- MPP challenge with an empty id
An MPP challenge carrying id="", which the draft says a server must never send.
Your client should Reject it, as the draft requires of every parser.
New to either protocol? Read what x402 and MPP put on the wire.
Build a custom testChoose the network, price, facilitator, and exactly how the endpoint should misbehave.