Behavior is a basic concern for humans. Behavior Driven Design is an abstract concept with various definitions agreed upon by the community of developers. The Behavior of our Teams has to change to practice Behavior Driven Development (BDD). Where is the payoff? Skilling up a team is annoying. Writing automated tests slows velocity and deliverables. Legacy concerns become black holes that keep your application stagnant. We'll look at how Behavior Driven Design and Development can address some of these concerns, and reduce friction for others. While there is no silver bullet, having a plan for how your code interacts, is generally better than not. BDD can help with evolving designs, ensuring objects answer questions, and encapsulating concerns to make boundaries more explicit. So let's dive into how to change our behavior so we can develop software that is easier to reason about.