Sandbox Environment Guide
This guide is for developers and QA testing their Meld crypto integration before going live. It covers what the sandbox is for, what it cannot do, which providers have usable sandboxes, and the supported test combinations. Note that the countries, tokens, fiat currencies, and payment methods supported in sandbox are a small subset of the ones supported in production. We recommend you only test in sandbox with the below combinations for the best results: Tokens- BTC
- ETH
- USDC
- US
- Europe
- CREDIT_DEBIT_CARD
- APPLE_PAY
- GOOGLE_PAY
- USD
- EUR
⚠️ Important: Sandbox Purpose and Limitations
What Sandbox is For
The sandbox environment is designed for:- Exploring transaction flows and understanding how the process works
- Testing UI integration and user experience
- Familiarizing yourself with provider interfaces
- Initial development and basic functionality testing
- Happy path combinations of the most widely used tokens
What Sandbox is NOT For
🚨 Critical Warning: The sandbox environment should NOT be relied upon for:- Coding solutions related to calculations
- Production data accuracy validation
- Finalizing business logic based on API responses
- Performance testing with accurate response times
- Coverage testing because onramp sandboxes are very limited in the tokens they support
🌍 Environment Access
| Environment | Widget URL | API Base URL |
|---|---|---|
| Sandbox | https://sb.meldcrypto.com | https://api-sb.meld.io |
| Production | https://meldcrypto.com | https://api.meld.io |
🏦 Sandbox-Friendly Providers
✅ Recommended for Testing (Full Sandbox Support)
These providers offer reliable sandbox environments ideal for testing:- Unlimit - Complete sandbox functionality with test cards
- Simplex - Reliable test environment with test wallet support
- TransFi - Good sandbox with specific test credentials
- Transak - Full-featured sandbox with test SSN/PAN numbers
- Sardine - Phone-based testing with predictable OTP system
⚠️ Limited Sandbox Support
These providers have sandbox limitations:- Banxa - Sandbox often rejects KYC/transactions; production testing recommended
- Stripe - Functions like production; requires real payment for full testing
- Paybis - Basic sandbox functionality
- BTC Direct - Limited sandbox features
❌ Production Only
These providers do not offer sandbox environments:- Robinhood - Production environment only
- Coinbase Pay - Production environment only
- Blockchain.com - Production environment only
- Alchemy Pay - Production-like sandbox requiring real payments
🔄 Flow Testing Capabilities
Buy Flow (Onramp)
- ✅ Fully testable end-to-end in sandbox
- Complete transaction simulation available
- Test cards and credentials work for most providers
- Recommended starting point for all integrations
Sell Flow (Offramp)
- ⚠️ Limited testing - quote generation only
- Cannot complete full transactions in sandbox
- Real cryptocurrency/fiat required for end-to-end testing
- Use for UI flow testing only
Transfer Flow
- ⚠️ Limited testing - configuration and quotes only
- Cannot execute actual transfers in sandbox
- Real wallet addresses required for testing
- Currently available in White-Label API only
🚀 Testing Best Practices
1. Start with Buy Flow
- Begin all integrations with buy flow testing
- Use recommended providers (Unlimit, Simplex, TransFi)
- Complete full transaction flow before moving to other flows
2. Provider Selection for Testing
- Choose providers from “Recommended for Testing” list
- Avoid production-only providers during initial development
- Test with multiple providers to understand variations
3. Sandbox Data Handling
- Never build calculation logic based on sandbox responses
- Use sandbox only for flow understanding and UI testing
- Validate all calculations and business logic in production
4. Progressive Testing Approach
🔧 Integration Testing Workflow
-
Sandbox Flow Testing
- Test UI integration
- Understand provider interfaces
- Validate basic functionality
-
Production Validation
- Test with real (small) transactions
- Validate calculation accuracy
- Confirm webhook functionality
-
Go Live
- Deploy with confidence
- Monitor real transaction data
- Iterate based on production insights
📞 Support
For sandbox-related questions or issues:- Check provider-specific testing credentials in the detailed testing guide
- Review flow limitations before troubleshooting
- Contact Meld support for integration guidance