Foundry FundMe

This repository is a simple FundMe dApp example built with Foundry.

The contract accepts ETH deposits only when the deposit is worth at least $5 USD, using a Chainlink ETH/USD price feed. The contract owner can withdraw the funds, and the contract supports both withdraw() and a gas-optimized cheaperWithdraw().

Project Overview

• src/FundMe.sol - Main funding contract
• src/PriceConverter.sol - Library to convert ETH to USD using Chainlink price feeds
• script/DeployFundMe.s.sol - Deployment script that uses HelperConfig to select the correct price feed address
• script/HelperConfig.s.sol - Local vs live network configuration, deploys a mock price feed for Anvil
• test/unit/FundMeTest.t.sol - Unit tests for funding and withdrawal behavior

Requirements

• Foundry installed
• forge, cast, and anvil available in your PATH

Setup

If the repository dependencies are not already installed, run:

forge install

Then build the project:

forge build

Run Tests

Run the full test suite:

forge test

Run only the FundMe unit tests:

forge test --match-contract FundMeTest

Local Development

Start a local node with Anvil:

anvil

Deploy locally using the script; HelperConfig deploys a mock ETH/USD feed automatically on Anvil:

forge script script/DeployFundMe.s.sol:DeployFundMe --broadcast --rpc-url http://127.0.0.1:8545 --private-key <PRIVATE_KEY>

Deploy to Sepolia (or another network)

Use a real RPC URL and private key. The deployment script will choose the correct price feed address for Sepolia.

forge script script/DeployFundMe.s.sol:DeployFundMe --rpc-url <RPC_URL> --private-key <PRIVATE_KEY> --broadcast

Contract Behavior

• fund() requires at least MINIMUM_USD worth of ETH, calculated using the Chainlink price feed
• withdraw() transfers the entire contract balance to the owner and resets funders
• cheaperWithdraw() performs the same action using a more gas-efficient loop
• fallback() and receive() both call fund() so sending ETH directly also funds the contract

Notes

• HelperConfig returns a live Chainlink feed address on Sepolia and Mainnet
• For local testing, it deploys a mock MockETHUSDAggregator with an initial price
• The contract stores funders and their funded amounts in mappings and arrays

Useful Commands

forge fmt
forge test
forge build
anvil

References

• Foundry docs: https://book.getfoundry.sh/
• Chainlink price feeds: https://docs.chain.link/data-feeds/