In software engineering, behavior-driven development (BDD) is an agile software development process that encourages collaboration among developers, quality assurance experts, and customer representatives in a software project. It encourages teams to use conversation and concrete examples to formalize a shared understanding of how the application should behave. It emerged from test-driven development (TDD). Behavior-driven development combines the general techniques and principles of TDD with ideas from domain-driven design and object-oriented analysis and design to provide software development and management teams with shared tools and a shared process to collaborate on software development. Although BDD is principally an idea about how software development should be managed by both business interests and technical insight, the practice of BDD does assume the use of specialized software tools to support the development process. Although these tools are often developed specifically for use in BDD projects, they can be seen as specialized forms of the tooling that supports test-driven development. The tools serve to add automation to the ubiquitous language that is a central theme of BDD. BDD is largely facilitated through the use of a simple domain-specific language (DSL) using natural-language constructs (e.g., English-like sentences) that can express the behaviour and the expected outcomes. Test scripts have long been a popular application of DSLs with varying degrees of sophistication. BDD is considered an effective technical practice especially when the "problem space" of the business problem to solve is complex. History Behavior-driven development, an extension of test-driven development, is a development process that makes use of a simple DSL. These DSLs convert structured natural language statements into executable tests. The result is a closer relationship to acceptance criteria for a given function and the tests used to validate that functionality. As such it is a natural extension of TDD testing in general. BDD focuses on: Where to start in the process What to test and what not to test How much to test in one go What to call the tests How to understand why a test fails At its heart, BDD is about rethinking the approach to unit testing and acceptance testing in order to avoid issues that naturally arise. For example, BDD suggests that unit test names be whole sentences starting with a conditional verb ("should" in English for example) and should be written in order of business value. Acceptance tests should be written using the standard agile framework of a user story: