Even the best test suites can't entirely prevent nasty surprises: race conditions, unexpected interactions, faults in distributed protocols and so on, still slip past them into production. Yet writing even more tests of the same kind quickly runs into diminishing returns. I'll talk about new automated techniques that can dramatically improve your testing, letting you focus on what your code should do, rather than which cases should be tested--with plenty of war stories from the likes of Ericsson, Volvo Cars, and Basho Technologies, to show how these new techniques really enable us to nail the hard stuff.