This document provides an overview of Behaviour Driven Development (BDD) using Behat and Drupal. It discusses what BDD is, the BDD workflow, how to write specification features and scenarios using Gherkin syntax, and how Behat reads Gherkin and runs tests through step definitions in context classes. It also covers how to integrate Behat and Drupal using the Drupal Extension, which provides pre-defined steps and contexts. The document demonstrates writing features and scenarios for downloading Drupal and provides examples of step keywords, results, and using Mink to control browser interactions without being concerned with the specific browser.