What is BDD?

Behavior-Driven Development (BDD) is a way of writing software where developers, testers, and business people describe how the software should behave in plain language. These descriptions are turned into automated tests that guide the coding process.

Let's break it down

  • Behavior: What the software does from the user’s point of view (e.g., “when I click the button, the form submits”).
  • Driven: The development work is guided by those behavior descriptions.
  • Development: The actual coding and testing of the software.
  • Plain language: Simple sentences written in everyday words, often using the “Given-When-Then” format, so non-technical folks can understand and contribute.

Why does it matter?

BDD keeps everyone-developers, testers, product owners-on the same page, reducing misunderstandings and rework. By turning requirements into executable tests, it catches bugs early and ensures the final product matches what users actually need.

Where is it used?

  • Building web applications where product owners want to verify features like login, checkout, or search behave correctly.
  • Mobile app development to confirm user flows (e.g., onboarding, push-notification handling).
  • API services where contracts between services are expressed as behavior scenarios.
  • Legacy system modernization, using BDD tests to document existing behavior before refactoring.

Good things about it

  • Improves communication between technical and non-technical team members.
  • Produces living documentation that stays up-to-date with the code.
  • Encourages test-first development, leading to higher code quality.
  • Makes regression testing easier because scenarios are automated.
  • Helps prioritize features based on real user behavior.

Not-so-good things

  • Requires time and effort to write and maintain clear scenarios, which can slow initial development.
  • Teams need training to write good BDD specifications; poor wording can lead to ambiguous tests.
  • Over-reliance on high-level scenarios may miss low-level edge cases.
  • Tooling and integration can be complex, especially in large, heterogeneous codebases.