Unittest why?

These weeks when i have some time i’am reading the book Introducing Visual Studio 2005 Team System by Richard Hundhausen. Well right now i’am at the chapter where the Test edition of the Team Suite is discussed. I think that Richard has a very good example why every project should make unittests. I’am a developer who is a proponent for unittests, but i also know some developers that are complaining that the creation of these tests is time consuming. Well if you have to persuade other developers use Richards example. He makes a comparison between a project with unittests and a car with brakes. Do brakes make you drive slower? NO they make you drive faster because you are confident that there is a way to stop. Well this is the same situation with unittest. Unittests can make you feel more confident to make changes to existing code. When you run the test and everything is still working well it means that you didn’t break anything. So developers use unittests