Welcome! # learncocotb.com is a place to learn cocotb - an open source coroutine-based cosimulation testbench environment for verifying VHDL and SystemVerilog RTL using Python. This site contains a book to learn cocotb by example as well as a collection of dev notes about how the internals of cocotb works for those interested in learning about the codebase. What can you do with cocotb? # Cocotb is a tool for writing testbenches to verify HDL.