Specification-Driven Development (SDD), also known as BDD 2.0, is a methodology where the product owner creates an executable specification in plain English that describes the functionality of a new feature, eliminating the need for additional test code. Unlike BDD 1.0, where specifications are created and then test code is written separately, SDD combines these steps, ensuring the specification runs and fails before feature development begins, akin to Test-Driven Development (TDD). This approach minimizes discrepancies between specifications and test code since the specification itself is executable, and it allows for the designation of reusable business rules similar to modular coding practices. An example using testRigor illustrates how specifications are structured in plain language to execute user actions, validate order completion, and confirm email delivery, demonstrating both the simplicity and effectiveness of SDD in streamlining the development process.