C++TESK is an open-source toolkit based on C++ and aimed to facilitate functional verification of RTL and system-level hardware designs. The core of the toolkit is a library of classes and macros defining the means for creating reference models (formal specifications), RTL adapters, random and FSM-based test scenarios, and test coverage metrics. Besides, the toolkit includes the report generator and tools for dynamic test parallelization on computer clusters and networks. Having been used in a number of industrial microprocessor verification projects, C++TESK proved its effectiveness in finding difficult bugs in real-life designs.