Behaviour Driven Development is an increasingly popular Agile practice that turns testing on its head, and involves a major shift in the role testers play in a project. Although popularly associated with automated acceptance testing and tools like Cucumber, BDD actually has much broader applications. In this talk, we will look at how Behaviour Driven Development radically changes the traditional tester role in Agile projects, and empowers them to tangibly contribute much more to the successful outcomes of the project. We will see how collaboratively discussing and defining acceptance criteria help reduce assumptions and errors in the early phases of the project, and help ensure that the features being built are well understood, testable, and valuable to the business. We will look at ways to write more effective, easier to maintain automated acceptance criteria, that free testers to do more productive testing tasks such as exploratory testing. And we will see how automated and manual acceptance test reporting can be combined to provide valuable progress, product documentation and release preparation reporting.