Ethereum testnets are essential for developers to test their applications and smart contracts in a safe environment without using real Ether. Below are some of the most commonly used Ethereum testnets, along with their features and sample code for interacting with them.

1. Ropsten

Ropsten is a proof-of-work testnet that closely resembles the Ethereum mainnet. It is often used for testing applications that require a realistic environment. However, it can be prone to congestion and spam attacks.

const ropstenProvider = new ethers.providers.InfuraProvider('ropsten', 'YOUR_INFURA_PROJECT_ID');

2. Kovan

Kovan is a proof-of-authority testnet that is known for its fast block times and stability. It is primarily used for testing decentralized applications and smart contracts.

const kovanProvider = new ethers.providers.InfuraProvider('kovan', 'YOUR_INFURA_PROJECT_ID');

3. Rinkeby

Rinkeby is another proof-of-authority testnet that is popular among developers. It is known for its stability and is often used for testing dApps and smart contracts.

const rinkebyProvider = new ethers.providers.InfuraProvider('rinkeby', 'YOUR_INFURA_PROJECT_ID');

4. Goerli

Goerli is a cross-client proof-of-authority testnet that is widely used for testing. It is stable and supports multiple clients, making it a good choice for developers.

const goerliProvider = new ethers.providers.InfuraProvider('goerli', 'YOUR_INFURA_PROJECT_ID');

5. Sepolia

Sepolia is a newer proof-of-stake testnet that is recommended for smart contract and application development. It is more stable than Goerli and is designed to be representative of the Ethereum mainnet.

const sepoliaProvider = new ethers.providers.InfuraProvider('sepolia', 'YOUR_INFURA_PROJECT_ID');

6. Holešky

Holešky is the newest Ethereum testnet, launched in September 2023. It aims to replace Goerli as the primary testnet for staking and protocol development, offering improved stability and a larger validator set.

const holeskyProvider = new ethers.providers.InfuraProvider('holesky', 'YOUR_INFURA_PROJECT_ID');

Conclusion

Each Ethereum testnet serves a unique purpose and offers different features for developers. By utilizing these testnets, developers can ensure their applications are robust and ready for deployment on the Ethereum mainnet.