View source for Property Based Developer Testing

Session at [[CITCONNA2013Sessions]]

Proposed by [[Paul Holser]]

* Amounts to adding "for-all" style assertions about a function to some "there-exists" style tests.
* Works best on already-TDD'ed code. TDD builds up designs example by example. Hard to see the "for-all" statements without data point to triangulate from.
* Agitar does something similar -- execute code using lots of different kinds of inputs, possibly deriving interesting data points by inspecting the test subject itself...
* Works well on already "math-y" domains
* Drives you, if you're paying attention, away from Primitive Obsession and modeling things like SKUs, Prices, SSNs, etc. as first-class concepts. Otherwise generators miss too much, or try to create invalid things.

= Literature =
* [http://natpryce.com/articles/000802.html Property Based TDD at SPA 2013]
* [http://shareandenjoy.saff.net/tdd-specifications.pdf The Practice of Theories: Adding "For-all" Statements to "There-exists" tests]
* [http://debasishg.blogspot.com/2012/07/property-based-testing-for-domain-models.html Property based testing for domain models]
* [http://blog.jessitron.com/2013/04/property-based-testing-what-is-it.html Property-based testing: What is it?]
* [http://book.realworldhaskell.org/read/testing-and-quality-assurance.html Real World Haskell: testing and quality assurance]
* [http://www.slideshare.net/FranklinChen/handout-18644963 Beyond xUnit exampled-based testing: property-based testing with ScalaCheck]
* [https://gist.github.com/npryce/4147916 Property-Based Testing Tools]
* [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.208.6016&rep=rep1&type=pdf Theory-infected: Or How I Learned to Stop Worrying and Love Universal Quantiﬁcation]

= Tooling: =

== Java ==
* [https://github.com/pholser/junit-quickcheck/ junit-quickcheck]
* [https://bitbucket.org/blob79/quickcheck QuickCheck]
* [http://www.jcheck.org/ JCheck]

== Scala ==
* [https://github.com/rickynils/scalacheck ScalaCheck]

== Python ==
* [https://github.com/DRMacIver/hypothesis Hypothesis]
* [https://github.com/dbravender/qc qc]

== Ruby ==
* [https://github.com/IKEGAMIDaisuke/rushcheck rushcheck]
* [https://github.com/hayeah/rantly rantly]

== Haskell ==
* [http://www.cse.chalmers.se/~rjmh/QuickCheck/ QuickCheck]

== Erlang ==
* [http://www.protest-project.eu/ ProTest]