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The sandbox

All integration testing happens against the UAT environment:
It’s a full replica of production wired to the payment gateway’s test environment — no real money moves. Use your sandbox client secret and signing key (they are different credentials from production).

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Test payments

On the sandbox payment page, use gateway test cards (your Float contact will supply the current set, including cards that trigger 3-D Secure challenges and declines). Walk through at minimum:
  • a successful payment on each instalment term you support,
  • a shopper cancel (click cancel on the payment page → expect a cancelled callback),
  • a declined card followed by a successful retry (expect a single successful callback — no notification for the decline),
  • an abandoned session (close the browser → checkout stays received).

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Testing callbacks locally

Expose your development server with a tunnel (ngrok, Cloudflare Tunnel) and pass the tunnel URL as notify_url, or simulate deliveries with curl.

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Go-live checklist

1

Callback handling is correct

  • X-Signature verified on every callback, constant-time comparison, raw-body based.
  • Handler is idempotent — duplicate deliveries cause no double-fulfilment.
  • Responds 2xx in under 10 seconds; slow work is deferred.
  • Fulfilment keys off the callback (or a GET /api/checkouts/:id check), never off success_url traffic.
2

Request signing is enabled

You’re sending a valid X-Signature on POST /api/checkouts and POST /api/refunds. Remember signing is sticky — once Float sees a signed request, unsigned mutations are rejected.
3

Amounts are correct

  • All amounts are integer pence.
  • The checkout amount equals what you’ll fulfil for — server-side calculated, never trusted from the browser.
  • Currency matches your merchant territory (GBP).
4

Edge cases are covered

  • Cancelled callbacks release stock/orders.
  • Stale received checkouts are treated as abandoned and reconciled.
  • The success_url page tolerates a not-yet-confirmed order (pending state, not an error).
5

Refunds work end-to-end

Create a partial and a full refund in sandbox and track them to complete. Confirm your admin tooling surfaces the refund-window errors (100-day limit, same-day rule on auto-refund integrations) sensibly.
6

Production configuration

  • Production client secret and signing key installed via your secret manager.
  • Base URL switched to https://secure.choosefloat.com.
  • notify_url points at your production endpoint with a valid TLS certificate.
  • Rate limits respected (see API overview) — in particular, merchant config is cached, not fetched per page view.
7

Run one live smoke test

Make a small real purchase, confirm the callback, fulfilment, and settlement reporting, then refund it (on auto-refund integrations, the refund can only be created after 10:00 the next day).

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Support

  • Integration questions: support@float.co.za
  • Include your merchant name, the environment, the checkout id, and timestamps with any issue report — Float logs every API request and callback delivery and can trace a payment end to end.