Unit testing, UI testing, and test-driven development (TDD) are explained. Unit testing tests individual units/blocks of code, UI testing automates user interactions, and TDD uses tests to design software. Visual Studio 2012 focuses the testing experience on developers with improvements to Microsoft Test (MS-Test) framework, support for additional frameworks like NUnit and Selenium, and features like continuous testing and code coverage analysis. Demo shows how to do UI testing with Selenium and practice TDD.