When testing off-ramp functionalities via API or Widget, you'll need testnet versions of cryptocurrencies. Here are common sources for obtaining them:

Blockchain	Test Asset	Source/Resource
Ethereum	Test USDC	Circle
Binance Smart Chain	Test USDT	Binance
Polygon	Test USDC	Circle
Base	Test USDC	Circle
Tron	Test USDT	Nileex
Solana	Test USDC	Circle
Optimism	Test USDC	Circle
Arbitrum	Test USDC	Circle
Celo	Test USDC	Circle