Too Long; Didn't Read
Tests are very important in daily development flow. Whenever you build a new feature or refactor existing one you want to be sure that you didn’t break something else. How can you be sure? You can ask your QA to commit regress but what if there are 10 developers more in your team? Right, QA will probably quit very soon. It’s even worse if your team does not have a QA, developers will simply keep breaking each other’s code. To prevent that, you can cover your code by tests and later on when you change something or add, and then all you need to do to be sure your code is still working is to run tests.