This document discusses test-driven development (TDD) and behavior-driven development (BDD). It describes how BDD uses conversations to discover requirements and build shared understanding. BDD captures conversations as executable specifications expressed in a common language. TDD follows the "Red-Green-Refactor" process of writing a failing test, adding code to pass the test, and refactoring code. TDD drives better design through incremental development guided by tests and prevents overdesign. While TDD can improve design, it also risks overly complex test code and dependencies if not kept simple. The document advocates starting with examples to guide development and testing in a test-driven manner.