Test-Driven Development

One of the foundational concepts of Agile software development is ensuring that your solution is loosely-coupled, highly-cohesive, and able to respond easily to changes; in this session we will explore the fundamentals of unit testing and their application through the practice of using TDD to evolve the design of your solution such that the results are both testable and flexible in the face of changing real-world requirements.

http://www.testingtv.com/2010/03/24/test-driven-development/