Building a Raffle DApp with Foundry + Chainlink (VRF + Automation)

After spending time learning Solidity using Foundry, I’ve just completed a practical project to consolidate my knowledge.
🎯 Project: Raffle DApp – A Decentralized Lottery Smart Contract
This project helped me apply core Web3 concepts in a real-world scenario.

🔗 Tech Stack Used
Chainlink VRF v2 — For verifiable, tamper-proof randomness

Chainlink Automation — To automate on-chain upkeep logic

Foundry — For testing, scripting, and deploying smart contracts

Solidity — Of course 😄

💡 How It Works
Users call enterRaffle() and send ETH to participate

At intervals, Chainlink Automation triggers performUpkeep() if conditions are met

Chainlink VRF returns a random number to select the winner

ETH is transferred to the selected wallet

✅ Key Improvement
To prevent spam and ensure fairness:
Each wallet is limited to 3 entries per round

This required additional validation logic and state tracking.

🧪 What I Learned
Writing secure logic to validate raffle states

Limiting wallet participation per round

Creating test scenarios for edge cases

Using HelperConfig to deploy across networks (localhost, Sepolia, etc.)

Automating VRF Subscription creation/funding

Mocking contracts, simulating time, improving test coverage

💻 Source Code
GitHub Repo:
🔗 https://github.com/ErwinPham/my-lottery-foundry
Contract (Deployed):
📜 0x48f945DEFA...F02889D7

🙏 Credit
Special thanks to @patrickalphac and the amazing course from Cyfrin Updraft for providing top-tier learning content!

🤝 Let’s Connect!
If you’re working on Web3, Solidity, Chainlink or Foundry — I’d love to learn and collaborate!

🏷️ Tags