DevLog250325

> Log Date: 250325

Devlog 250325: Understanding Ethereum Testnets and Their Currencies

Overview

Today I focused on learning how Ethereum testnets work, why we use them, and what currencies power them. This is essential knowledge for any smart contract developer, especially while building and testing dApps like the Metaverse Sandbox.

Testnets provide a safe and cost-free environment to test smart contracts before deploying to the mainnet. They simulate blockchain environments using separate consensus mechanisms and fake currencies to avoid real-world financial consequences.

What Is a Testnet?

A testnet is a public or private blockchain that mirrors the functionality of a main blockchain (mainnet), but is isolated for testing purposes.

Why Use a Testnet?

Avoid using real ETH or tokens
Test smart contracts and UI interactions
Estimate gas costs in a real environment
Debug transaction flows, wallet behavior, and deployment scripts

Popular Ethereum-Compatible Testnets (2024–2025)

Testnet Name	Chain ID	Use Case	Native Token
Sepolia	11155111	Main Ethereum testnet (replaces Goerli)	ETH (testnet)
Amoy	80002	Polygon PoS L2 (replaces Mumbai)	POL (testnet)
Holesky	17000	Ethereum consensus layer testing	ETH (testnet)
Chiado	10200	Gnosis Chain testnet	xDAI
Scroll Alpha	varies	Zero-knowledge Layer 2 for Scroll	ETH (testnet)
Arbitrum Sepolia	varies	Optimistic rollup L2 for Arbitrum	ETH (testnet)

Currency on Testnets

Each testnet uses a test version of a native token to simulate transactions.

Key Concepts:

Test ETH, MATIC, POL, or xDAI are not real assets.
These tokens are obtained through faucets (web apps that send small test amounts).
You still need these test tokens to pay gas fees, just like on mainnet.

How to Get Testnet Tokens

Testnet	Faucet URL	Notes
Sepolia	https://sepoliafaucet.com/	Requires GitHub login
Amoy (Polygon)	https://faucet.polygon.technology/	Requires developer form
Chiado (Gnosis)	https://gnosisfaucet.com/	Fast and open
Arbitrum Sepolia	https://faucet.quicknode.com/arbitrum/sepolia	New L2 faucet

Some testnets (like Amoy) require mainnet POL before giving out testnet POL, which can create onboarding headaches.

Differences Between Testnets

Feature	Sepolia	Amoy (Polygon)	Chiado	Arbitrum Sepolia
L2 Support	No	Yes	No	Yes
Realistic Gas Simulation	Medium	High	Low	High
Tooling Support	Excellent	Growing	Moderate	Good
Token Availability	Easy (faucets)	Moderate (email)	Easy	Moderate

How They Work Behind the Scenes

Each testnet runs its own consensus (PoA, PoS, or L2 rollup mechanics).
Block explorers like Sepolia Etherscan or Amoy Polygonscan let you monitor transactions.
Tools like Foundry, Hardhat, and Truffle all support testnet deployments with correct --rpc-url settings.

Example RPC config for Sepolia:

forge script script/Deploy.s.sol --rpc-url https://sepolia.infura.io/v3/YOUR_API_KEY --private-key $PRIVATE_KEY --broadcast

Takeaways

Testnets are vital for safe and efficient smart contract development.
Choosing the right testnet depends on your target deployment chain, availability of faucets, and desired simulation accuracy.
Always monitor the gas costs and contract behavior on testnets before pushing to mainnet.

Next Steps

Continue testing MetaverseLand contracts on Amoy using the 100 testnet POL I received yesterday.
Create a script that checks testnet balances, faucet availability, and network status for fast switching between environments.
Document the full deployment pipeline for Foundry + Polygon Amoy for repeatability.

This devlog helps solidify my understanding of the ecosystem of testnets and prepares me for scaling my Web3 deployments with confidence.