The Internet protocol specifications are instructions designed for engineers to build things, with great care taken to ensure document quality through consensus and review from experts in the field. The standardization process is crucial for the reliability and security of the Internet. h3i is a binary command line tool and Rust library designed for low-level testing and debugging of HTTP/3, which runs over QUIC. It provides a flexible framework for testing and can be used to test various aspects of the protocols, including stream data split into STREAM frames sent in QUIC packets over UDP. The h3i tool allows users to exercise servers by sending malformed requests or invalid frame sequences, helping to determine if a server is acting robustly and defensively. It provides an interface for users to interactively input their own tests, with the ability to record and replay test cases using qlog. This makes it easier for developers to take advantage of h3i's capabilities, particularly for those who are not experts in protocol testing or Rust.