Summary
BDD is a collaborative development methodology that bridges the gap between technical tests and business requirements by expressing behaviour in a shared language understood by developers, testers, and product stakeholders.
What is BDD?
Introduced by Dan North as an evolution of TDD, BDD focuses on describing the behaviour of a system rather than testing its implementation. Scenarios are written in a structured natural language—typically Gherkin's Given/When/Then syntax—that all team members can read and contribute to.
These scenarios serve as both documentation and executable tests. Tools like Cucumber (Java, Ruby), Behave (Python), and RSpec (Ruby) parse Gherkin scenarios and map them to step definitions that drive the application.
BDD encourages conversations between developers, QA, and business stakeholders (the "Three Amigos") before implementation begins, reducing misunderstandings and rework.
Why is BDD relevant?
- Shared understanding: Gherkin scenarios create a single source of truth readable by both business and technical teams
- Living documentation: Passing scenarios prove features work as specified; they evolve alongside the codebase
- Collaboration: Three Amigos sessions surface ambiguities early, reducing costly late-stage defects