This is a course for developers, designed to bring about a fundamental change to the way developers go about their day-to-day business of writing software code. Instead of thinking about unit tests as at best an afterthought, having already written the application code, the course aims to turn this practice on its head, and get programmers to write tests before the code to be tested.Originating in the Agile methodology of Extreme Programming, Test Driven Development (TDD) has become accepted as a mainstream best practice, and is being adopted by major organisations as a means of improving code quality and developer productivity. Because Test Driven Development involves such a major inversion of most developers' ways of thinking and working, the course is strongly exercise based . Typically developers find TDD initially strange, but go on to find it quite liberating, and become 'test infected' (unable to write code without having first devised unit tests.) The exercises are based on the C# programming language using Visual Studio, MSTest, NUnit2,Nunit3, Xunit, NCrunch, Moq, Fluent Assertions and Specflow. All of these operating in a client-only GIT environment.