This paper introduces PANTHER, a modular framework for testing network protocols and formally verifying their specification, as detailed in our FORTE'24 article. PANTHER supports plugins for testing modules, Implementations Under Test (IUTs), network environments (e.g. Shadow, Docker), and execution environments (e.g., strace, gperf). Its modular design validates complex protocol properties, adapts to dynamic behaviors, and facilitates seamless plugin integration for scalability. Using Ivy as its first testing module and Shadow for reproducible simulations, PANTHER enables tailored experiments, precise model-based testing, and reliable IUT validation in complex and custom network environments.