Are you doing Test-Driven Development or Bug Driven Development? From my experiences, test-driven development seems to slow you down at the beginning of a project. This isn't entirely true, it just feels that way. When you can overcome this and keep hanging on, the benefits become apparent when going towards the end of the project. You have only a few bugs to solve (if any), and everything seems to fit perfectly. No more debugging sessions that seem to take forever, no more working long hours and you are confident to make changes based on the feedback of your customers just because you have a ton of unit tests to back you up. How is that for an argument?