Experiences with QuickCheck: Testing the Hard Stuff and Staying Sane

This is not a typical scientific paper. It does not present a new method, with careful experiments to evaluate it, and detailed references to related work. Rather, it recounts some of my experiences over the last 15 years, working with QuickCheck, and its purpose is as much to entertain as to inform. QuickCheck is a random testing tool that Koen Claessen and I invented, which has since become the testing tool of choice in the Haskell community. In 2006 I co-founded Quviq, to develop and market an Erlang version, which we have since applied for a wide variety of customers, encountering many fascinating testing problems as a result. This paper introduces Quviq QuickCheck, and in particular the extensions made for testing stateful code, via a toy example in C. It goes on to describe the largest QuickCheck project to date, which developed acceptance tests for AUTOSAR C code on behalf of Volvo Cars. Finally it explains a race detection method that nailed a notorious bug plaguing Klarna, northern Europe’s market leader in invoicing systems for e-commerce. Together, these examples give a reasonable overview of the way QuickCheck has been used in industrial practice.