The idea of unit testing has been around for many years. Test early, test often is a mantra that concerns unit testing as well.

Integrate Hamcrest and Mockito with JUnit 5 for more sophisticated unit testing with assertions, simulations, and behavior verification using Mockito spies.

Peter tries out Visual Studio Enterprise 2017's Live Unit Testing and has what might be a life-changing experience.

It’s a powerful way of testing for early startups because we can replicate what the user is expected to do and make sure that the system is behaving as expected.