BDD Methodology for Acceptance Test Design

Core Philosophy

Test units of behavior, not units of code. Acceptance tests validate business outcomes through public interfaces, decoupled from implementation.

Outside-In Double-Loop TDD

The acceptance-designer creates the outer loop of Outside-In TDD. Development starts from user perspective, drives inward.

Outer loop (acceptance/BDD): Hours to days | User perspective, business language | Defines "done" | Scenarios describe user goals and observable outcomes, not internals | Failing outer-loop test is the starting signal for implementation

Inner loop (unit/TDD): Minutes | Developer perspective, technical terms | Software-crafter owns this loop