18 Stochastic and Property-Based Testing 

random guessing a.k.a. Monkey testing
Maybe not the best tests, but easy to generate, and fast to run!

What are the properties you want the test data to have?
Let the computer (or the monkees) generate random test data with those properties

Smart, Dumb, Evil, and Chaos Monkeys 
dumb-pretty much random; most tests uninteresting
smart-more likely to actually be entered by user 
(if not correct input, then input that could be typed by a human)
evil-a malicious user (black hat hacker)
chaos—randomly shut down systems 

mutation testing
play randomly with code to make sure errors ARE caught
if mutation is benign how important is the code?