Test your integration - Lynq Docs

Test the same path your customers will use: order creation, the Payment Intent, browser Checkout, webhook verification, and fulfilment.

Test cards

Test mode is simulated by Lynq, so it needs no bank or wallet credentials. Use any future expiry date, any three-digit security code, and any cardholder name. The card number decides the result:

Card number	Result
`4242 4242 4242 4242`	The payment succeeds.
`4000 0000 0000 0002`	The card is declined: `requires_payment_method` with `card_declined`.
`4000 0000 0000 9995`	The payment stays `processing`.

Any other valid card number succeeds. Idram and Apple Pay appear in test checkouts so you can see the whole form, but they can’t be paid yet. Choosing one and paying shows a notice; use a test card instead.

Scenarios to cover

Scenario	Browser expectation	Server expectation
Successful Card payment	Checkout completes and reports `succeeded` or a pending transition before completion.	A verified success webhook marks the order paid once.
Card declined or invalid	Checkout reports `requires_payment_method` with display-safe text.	The order remains unpaid and can accept another attempt.
Customer closes the page	No irreversible browser-side action occurs.	A later webhook can still complete the order if payment succeeded.
Duplicate webhook	Customer-visible state does not change twice.	The event ID is recognized and fulfilment runs once.
Temporary webhook failure	Payment may look complete in Dashboard while delivery retries.	The receiver returns `5xx`, recovers, and processes a retry.

Webhook tests

Send a Test mode event from Dashboard → Webhooks and confirm the receiver verifies Lynq-Signature against the raw body.
Replay the same request and confirm it returns 2xx without repeating fulfilment.
Send an invalid signature and confirm it is rejected.
Return 500 temporarily, confirm the delivery moves to retrying, then restore the receiver and confirm a later delivery succeeds.

Testing is complete when a payment updates the correct order exactly once through a verified webhook, including after the browser closes and after a webhook retry.

Continue with the go-live checklist.

Last modified on November 11, 2026