Property-based testing (PBT) validates the expected behavior of a system by checking it against a range of data points. A well-chosen set of properties will give the user a lot of confidence that the system is behaving as expected. The idea is that when the code is modified, failures in the tests reveal problems that would not have been found otherwise. This talk will cover the basic principles and several examples of PBT, using the jqwik library.

PBT allows you to define invariants (like reversing a list twice should result in the original list) and verify that they hold given generated changes that include a wide range of random inputs, including edge and corner cases. The jqwik library works well with JUnit to provide an important part of your testing strategy.