Detailed Instructions

Begin by installing the Foundry toolkit, which includes Forge, Cast, Anvil, and Chisel. This is the primary framework for developing, testing, and deploying smart contracts. Use the following command to install Foundry:

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curl -L https://foundry.paradigm.xyz | bash
foundryup

• Sub-step 1: Verify the installation by running forge --version and anvil --version.
• Sub-step 2: Install Node.js (version 18 or later) and npm from the official website or using a version manager like nvm.
• Sub-step 3: Confirm Node.js is installed with node --version and npm --version.

Tip: Using nvm allows you to easily switch between Node.js versions for different projects.

Detailed Instructions

Create a new Foundry project, which will generate a standard directory structure with src/, test/, and script/ folders. Run forge init my-l2-defi-project. Navigate into the project directory. The critical step is adding dependencies for Layer 2 development. You will need libraries for common standards and testing utilities.

• Sub-step 1: Install the OpenZeppelin Contracts library: forge install OpenZeppelin/openzeppelin-contracts.
• Sub-step 2: Add the solmate library for gas-optimized contracts: forge install transmissions11/solmate.
• Sub-step 3: For specific L2 tooling, add forge-std for enhanced testing: forge install foundry-rs/forge-std.

Update your foundry.toml file to remap these dependencies for easier imports in your Solidity files.

tomlCopy
# Example remapping in foundry.toml
remappings = [
    '@openzeppelin/=lib/openzeppelin-contracts/',
    '@solmate/=lib/solmate/src/',
    '@forge-std/=lib/forge-std/src/'
]

Detailed Instructions

Use Anvil, Foundry's local testnet node, to simulate a Layer 2 environment. The most effective method is to fork a live L2 network like Arbitrum or Optimism. This gives your local environment access to real contract states and prices. Start Anvil with a forking command.

• Sub-step 1: Obtain a free RPC URL for your target L2 from a provider like Alchemy or Infura.
• Sub-step 2: Launch Anvil with the fork: anvil --fork-url https://arb1.arbitrum.io/rpc.
• Sub-step 3: Note the RPC endpoint (usually http://127.0.0.1:8545) and the private keys of generated accounts printed in the terminal.

This creates a local sandbox where transactions are instant and free. You can impersonate any account and manipulate blockchain state for complex testing scenarios.

Tip: Use the --fork-block-number flag to fork from a specific block, ensuring consistent test results.

Detailed Instructions

Create a basic DeFi contract, such as a mock ERC-20 token or a vault. Place it in src/. Write a corresponding test file in test/ using Solidity and Forge's testing framework. The test should deploy the contract to your local Anvil instance and verify its logic.

• Sub-step 1: In src/MyToken.sol, write a simple contract that inherits from OpenZeppelin's ERC20.
• Sub-step 2: In test/MyToken.t.sol, import the contract and forge-std. Use the vm.startPrank cheatcode to simulate user transactions.
• Sub-step 3: Run the test with forge test --fork-url http://localhost:8545 -vvv to see detailed logs.

solidityCopy
// Example test snippet
import "forge-std/Test.sol";
import "../src/MyToken.sol";

contract MyTokenTest is Test {
    MyToken token;
    function setUp() public {
        token = new MyToken();
    }
    function testMint() public {
        vm.prank(address(0x1));
        token.mint(address(this), 100e18);
        assertEq(token.balanceOf(address(this)), 100e18);
    }
}

Verify the tests pass, confirming your environment is functional.

Detailed Instructions

For full-stack development, set up a frontend to interact with your contracts. Initialize a Next.js project with TypeScript and install essential Web3 libraries. Configure it to connect to your local Anvil node.

• Sub-step 1: Create a new Next.js app: npx create-next-app@latest frontend --typescript --tailwind --app.
• Sub-step 2: Install dependencies: wagmi, viem, and @rainbow-me/rainbowkit.
• Sub-step 3: Configure the Wagmi client in your app to use the local Anvil RPC URL (http://127.0.0.1:8545) and the chain ID (usually 31337).

Create a component that reads the balance of your deployed token. Use Viem's createPublicClient and createWalletClient for direct interactions. This setup allows you to test the complete user flow from the browser.

Tip: Use hardhat_impersonateAccount RPC method via Viem to control funded accounts in your frontend for testing transactions without real gas.

Detailed Instructions

Begin by initializing a new project using a framework like Hardhat or Foundry. Configure your hardhat.config.js or foundry.toml to include the target Layer 2 network. You must add the network's RPC endpoint and a funded private key for deployment. For example, to add Arbitrum Sepolia, specify the RPC URL https://sepolia-rollup.arbitrum.io/rpc and chain ID 421614. Install necessary plugins for verification, such as @nomicfoundation/hardhat-verify. This setup ensures your compiler version matches the target network's EVM compatibility and that you have the correct dependencies for contract interaction.

• Sub-step 1: Run npm init -y and install hardhat
• Sub-step 2: Add network configuration for your chosen L2 (e.g., Optimism, Base)
• Sub-step 3: Set the Solidity compiler version to 0.8.20 in hardhat.config.js

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// Example hardhat.config.js network entry
module.exports = {
  networks: {
    'optimism-sepolia': {
      url: 'https://sepolia.optimism.io',
      accounts: [process.env.PRIVATE_KEY]
    }
  }
};

Tip: Use environment variables (dotenv) to manage your private keys and API keys securely, never commit them to version control.

Detailed Instructions

Run the compiler to generate bytecode and ABI artifacts. For Hardhat, execute npx hardhat compile. This step validates your Solidity syntax and checks for compilation errors specific to the L2 environment, such as opcode support. Next, write and run comprehensive tests using the local Hardhat Network or a forked version of the L2. Testing should cover core DeFi logic like token transfers, liquidity provisioning, and fee calculations. Use console.log in Solidity (via hardhat/console.sol) for debugging. Ensure your tests pass with npx hardhat test. This pre-deployment verification catches logical errors and saves on gas costs from failed deployments.

• Sub-step 1: Execute npx hardhat compile and inspect artifacts in /artifacts
• Sub-step 2: Write unit tests for all public and external functions
• Sub-step 3: Run tests with npx hardhat test --network hardhat

solidityCopy
// Example test snippet checking a mint function
function testMint() public {
    uint256 initialSupply = token.totalSupply();
    token.mint(msg.sender, 100e18);
    assertEq(token.totalSupply(), initialSupply + 100e18);
}

Tip: Fork the mainnet L2 state using an RPC provider like Alchemy to test against real contract interactions and balances.

Detailed Instructions

Create a deployment script that uses the deployer account configured in your environment. The script should handle constructor arguments, which for a DeFi protocol might include an initial admin address or a fee percentage. Run the deployment using the command npx hardhat run scripts/deploy.js --network optimism-sepolia. Monitor the transaction in a block explorer like Arbiscope or Optimism Sepolia Explorer. Confirm the deployment was successful by checking the contract creation transaction and noting the new contract address. This step consumes testnet ETH, which you can obtain from a faucet. Verify the contract's initial state matches expectations by making a simple view function call.

• Sub-step 1: Write a script that calls deploy() on your contract factory
• Sub-step 2: Run the deploy command and wait for confirmation
• Sub-step 3: Copy the deployed contract address from the terminal output

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// Example Hardhat deployment script
deployScript = async () => {
  const MyContract = await ethers.getContractFactory('MyDeFiVault');
  const contract = await MyContract.deploy('0x...Admin', 500); // 5% fee
  await contract.waitForDeployment();
  console.log('Contract deployed to:', await contract.getAddress());
};

Tip: Save the deployment address and constructor arguments to a file for easy reference during verification and frontend integration.

Detailed Instructions

Contract verification is critical for user auditability. Use the Hardhat Etherscan plugin with the command npx hardhat verify --network optimism-sepolia <DEPLOYED_ADDRESS> 'ConstructorArg1' 'ConstructorArg2'. You must have an API key from the block explorer (e.g., Etherscan, Arbiscan) configured. The plugin will compile the source code, upload it, and attempt to match the deployed bytecode. For complex deployments with libraries or proxy patterns, you may need to provide additional parameters like --constructor-args. After successful verification, the explorer will display a 'Contract Source Code Verified' badge, allowing users to read the code and interact with functions directly via the UI.

• Sub-step 1: Obtain an API key from the relevant block explorer portal
• Sub-step 2: Run the verify command with the correct address and arguments
• Sub-step 3: Check the explorer page to confirm the code is visible

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# Example verification command for a contract with two arguments
npx hardhat verify --network arbitrum-sepolia 0x742d35Cc6634C0532925a3b844Bc9e0a3A123456 \
  '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4' \
  1000

Tip: For upgradeable proxies, verify both the proxy contract and the implementation contract separately. Use the --proxy flag if supported by the explorer.

Detailed Instructions

After verification, conduct on-chain integration tests. Use a script or a tool like cast (Foundry) or hardhat console to call key functions. For a DeFi contract, test depositing funds, swapping tokens, or checking accrued interest. Confirm that event logs are emitted correctly and that state changes are accurate. Check for any unexpected reverts due to L2-specific gas or block parameters. This is also the stage to set up monitoring by adding the contract address to a service like Tenderly or OpenZeppelin Defender. Finally, ensure all administrative functions (e.g., pausing, fee updates) are accessible only by the authorized owner address, completing a security check before considering a mainnet deployment.

• Sub-step 1: Use npx hardhat console --network base-sepolia to connect and call functions
• Sub-step 2: Execute a sample transaction, like a deposit of 0.1 test ETH
• Sub-step 3: Query the contract state to confirm the transaction succeeded

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// Hardhat console interaction example
const contract = await ethers.getContractAt('IVault', '0xDeployedAddress');
await contract.deposit({ value: ethers.parseEther('0.1') });
const balance = await contract.getBalance(await ethers.provider.getSigner().getAddress());
console.log('New balance:', balance.toString());

Tip: Simulate transactions using Tenderly before executing them to estimate gas and identify potential failures without spending funds.