NST: A unit testing system for Common Lisp

We introduce NST, an expressive and extensible unit testing framework for Common Lisp. Distinct features of Lisp's object system CLOS allow an elegant implementation for NST, and we describe this class model and implementation. There are over a dozen test frameworks for Lisp which are currently available, almost half of which are under active maintenance, and we compare these packages' features. Development of NST is ongoing, and we conclude with a discussion of future directions for the system.