The document discusses test-driven development (TDD) and how it can be used to reduce unnecessary complexity, also known as inventory, in software design. TDD involves writing automated tests before code to articulate requirements and ensure only needed code is written. It promotes designing simple, clear code without duplication through principles like You Aren't Gonna Need It and refactoring code in small, reversible steps. Following TDD principles is claimed to reduce inventory created by excess complexity and allow designs to evolve incrementally based on test feedback.

1. Test-driven Design/Development