Developer shares three key lessons from building an NFT marketplace with Foundry

A developer building an NFT marketplace in Solidity using Foundry and OpenZeppelin documented three critical lessons learned during the project. The first lesson was that working code is not necessarily secure code, as functions can operate correctly while still being vulnerable to exploits. The second takeaway was that smart contract architecture matters early on, with clear separation of responsibilities across contracts making code easier to maintain and audit. Third, the developer found that testing should go beyond happy-path scenarios to simulate how malicious users might manipulate contract behavior. The overall conclusion was that smart contract quality depends not just on functionality, but on how the code holds up when actively challenged.