HUnit is a unit testing framework for Haskell, inspired by the JUnit tool for Java. This guide describes how to use HUnit, assuming you are familiar with Haskell, though not necessarily with JUnit. A test-centered methodology for software development is most effective when tests are easy to create, change, and execute. The JUnit tool pioneered support for test-first development in Java. HUnit is an adaptation of JUnit to Haskell, a general-purpose, purely functional programming language. (To learn more about Haskell, see With HUnit, as with JUnit, you can easily create tests, name them, group them into suites, and execute them, with the framework checking the results automatically. Test specification in HUnit is even more concise and flexible than in JUnit, thanks to the nature of the Haskell language. HUnit currently includes only a text-based test controller, but the framework is designed for easy extension. (Would anyone care to write a graphical test controller for HUnit?)