Payment Gateway Testing Scenarios for a Crypto On-Ramp

• The scenarios to test cover what users see (a declined card, an identity check, a short wait) and what your team sees (purchase records and exports).
• Our sandbox copies the production purchase flow. Its test cards approve or decline on request, identity checks return set outcomes, and test networks cover Bitcoin and Ethereum, including USDT.
• Our launch process ends with a small purchase in production, because production brings in the user's bank and wallet.
• A dedicated integration manager supports sandbox testing and launch.

A copy of the payment service where no money changes hands. It has test cards that approve or decline on request, test blockchain networks where coins have no value, and a dashboard where test purchases can be reviewed.

Production is the live service, where users pay with their own money.

The sandbox is the first part of an on-ramp your teams will use, so compare it alongside fees and coverage. A good one shows them the purchase as users will see it, so fewer questions stay open at launch.

A first purchase runs from your branded checkout through payment and identity verification, and it may include a short wait for that check. Product can review each of these steps in our sandbox before launch.

Product will want the checkout to look like the rest of your app. Our widget can be themed to match your brand, including your logo on the login screen, so product can review your branded checkout before launch.

The integration method also shapes what users see. The widget can open through a redirect, sit inside your page, or run in your iOS or Android app, and the sandbox has its own addresses for the redirect and embedded versions.

Product can therefore test the method you plan to launch with, starting from the screen you choose. The widget can open with the crypto and amount already selected, so the first screen matches the offer in your app.

When a card payment fails, our Try Again feature gives users a second attempt inside the widget without starting over. A dedicated integration manager sets whether users can change the amount or payment method and how many retries they get.

A payment can stop for reasons such as insufficient funds or a bank's decision, and our sandbox lets product see that moment before launch. One test card succeeds or fails on request, so product can review the decline screen and the retry.

We run identity verification (KYC, or Know Your Customer) on our side as merchant of record. During this check, first-time buyers may be asked for an ID document and a selfie, so product should review the screens around it before launch.

The sandbox can produce an approved verification or a request to upload a document again, and it includes the selfie step, so product sees each outcome before users do.

Smaller first purchases can follow a shorter path. With Fast Track, eligible new users buy crypto without full verification while their combined purchases and sales stay below €700, and product can review this journey next to full verification.

A purchase can pause while the user completes identity verification. In the sandbox, product can review what users read during that wait and which screen they see afterwards.

In production, users get 30 minutes and an email link to finish verification, and the purchase goes through once the check is complete. Your in-app messages during the wait can reflect this timing.

Support and finance handle purchase questions and reconciliation after launch, so they need to see the flow first. The sandbox includes a dashboard where both teams can practice on test purchases.

For support, the test is finding a specific purchase from the details a user would give. Our Merchant Dashboard shows transactions as they happen, so agents can practice this before launch.

Alongside your agents, our Customer Support answers your users 24/7 by live chat and email, so purchase questions have a second line of help.

Finance needs to match each purchase to an order. In our transaction records, a completed card purchase also creates a second record for sending the crypto to the user's wallet.

A cancelled purchase, by contrast, is marked as cancelled, with funds returned if the card was charged. Finance can check both cases on test purchases before the first live sale.

In addition, we take responsibility for chargebacks and disputes as merchant of record, so the finance team's work stays focused on matching orders.

In production, the user's bank reviews each card payment and can ask for an extra confirmation, such as an approval in the banking app. We support 3D Secure, the security layer banks and card issuers use for this confirmation on online card payments.

Banks keep this step in place because it protects card payments. A December 2025 joint report by the European Banking Authority and the European Central Bank found that strong customer authentication remains effective, especially for card payments.

A small live purchase in production confirms the remaining parts of the flow:

• The user's bank approves the payment, including any 3D Secure step
• Crypto reaches the user's wallet
• Your live account settings work as planned

For these reasons, our launch process ends with a small test purchase in production.

If your users will also sell crypto for money (off-ramp), an integration manager switches it on, and a small live sale checks that flow too. We verify the user's identity on every sale.

Sandbox access comes at the start of onboarding, so your teams can review the purchase before any user sees it. The same integration manager stays with you until go-live, and after launch you have a dedicated success manager and our Merchant Support team.

If you're planning to add a crypto on-ramp, tell us how you want your users' first purchase to look. Our team will set up sandbox access and test that flow together with you, so on launch day your teams already know what the user will see.

What are the main payment gateway testing scenarios? For a crypto on-ramp, product tests a declined card and retry, identity verification, and a purchase waiting for verification. Support and finance test finding a purchase in the dashboard and matching records. A small live purchase then covers the steps that need a live card.

What should a payment gateway sandbox environment include for testing? Test cards set to succeed or fail and identity checks with set outcomes, plus test blockchain networks and a dashboard to review test purchases. Our sandbox includes all four.

Which platform has a better sandbox for fiat and crypto? Look for a sandbox that follows production closely and covers the coins you plan to offer. Mercuryo's sandbox mirrors the production purchase flow and supports test purchases on Bitcoin and Ethereum networks.

Can we test a declined payment in sandbox? Yes. Our sandbox has a test card that fails on request, so product can review the decline screen and the Try Again retry options.

Can we test stablecoin purchases in sandbox? Yes. Our sandbox supports USDT purchases on an Ethereum test network, and once you go live, our on-ramp offers USDT on 8 networks and USDC on 10.

How do we test a crypto on-ramp integration in production safely? Our launch process closes with one small live purchase before full launch, after our team has tested the integration together with yours.