Test-Driven Development has become deservedly popular in the past decade, with easy-to-use xUnit unit testing frameworks leading the way toward encouraging developers to write tests. But xUnit has limitations: how does one know one has written enough test cases for a desired behavior? And what if the behavior is conditional on other behavior? Property-based testing, first popularized for Haskell with the QuickCheck library, but available now for other languages as well, offers a powerful addition to one's testing toolkit.
I will discuss the concepts of property-based testing and illustrate them concretely using ScalaCheck for Scala, and point toward similar test frameworks in other languages.