This document discusses Acceptance Test Driven Development (ATDD), Behavior Driven Development (BDD), and Test Driven Development (TDD). ATDD uses automated acceptance tests defined early in development to ensure all stakeholders understand requirements. BDD uses a Given/When/Then framework to define automated acceptance tests that assert system functionality. SpecFlow is a tool that allows testers, analysts, and developers to collaborate on BDD feature files and step definitions. TDD involves writing automated tests before code to improve quality and support refactoring through the "Red-Green-Refactor" cycle. The document demonstrates SpecFlow with an example of a movie ticketing system.