Behavior Driven Development

Behavior Driven Development, or BDD, bridges business requirements with automated tests. Requirements are expressed in a shared, natural language that developers, testers, and business stakeholders all understand. BDD reduces misunderstandings and creates a common view of desired system behavior.

In a Nutshell

• BDD describes behavior in natural language using the Given-When-Then format.
• It encourages collaboration between business, development, and QA teams.
• Tools like Cucumber, SpecFlow, and Behave translate scenarios into executable tests.
• BDD is not a testing method but a communication and development practice.

Core Concept

BDD evolved from TDD and focuses on software behavior from a business perspective. Instead of describing technically what a method should return, examples are written in the user’s language. These examples become tests that serve simultaneously as specification and living documentation.

The Given-When-Then Schema

Given

Describes the initial state or preconditions for a scenario.

When

Describes the action being performed.

Then

Describes the expected result or system response.

Example Scenario

Scenario: Customer receives discount on large purchase

Given a customer has items worth 200 euros in their cart
When the customer proceeds to checkout
Then the total amount should be reduced by 20 euros

Key Tools

• Cucumber: Popular BDD framework for Java, Ruby, JavaScript, and many other languages.
• SpecFlow: BDD framework for .NET.
• Behave: BDD framework for Python.
• Serenity BDD: Cucumber extension focused on reporting.
• Gauge: Lightweight BDD alternative from ThoughtWorks.

Practical Example: Cucumber Feature for an Order Process

Feature: Discount calculation

  Scenario: Standard discount from 100 euros
    Given the cart contains items worth 100 euros
    When the customer starts the checkout process
    Then a discount of 10 euros is applied
    And the new total is 90 euros

  Scenario: No discount below 100 euros
    Given the cart contains items worth 50 euros
    When the customer starts the checkout process
    Then no discount is applied
    And the total remains 50 euros

Strengths and Weaknesses

Strengths

• Shared language: Business and development teams discuss the same examples.
• Clear requirements: Misunderstandings are caught before implementation.
• Living documentation: Scenarios provide an understandable record of system behavior.
• Focus on business value: Tests align with business goals rather than implementation details.

Weaknesses

• Effort: Creating and maintaining scenarios takes time.
• Complexity: Large feature files can become hard to navigate.
• Stakeholder dependency: Without regular business involvement, BDD loses its impact.
• Maintenance burden: Poorly maintained step definitions can cause technical debt.

Exam Essentials

• Definition and purpose of BDD.
• The Given-When-Then format.
• Difference between BDD and TDD.
• Roles of business, development, and QA.
• Common tools: Cucumber, SpecFlow, Behave.

Typical Exam Questions (with Brief Answers)

1. What is BDD? A practice that describes business behavior in natural language and uses it as executable tests.

2. What does Given-When-Then mean? It describes the precondition, action, and expected outcome of a scenario.

3. Name a BDD tool. Cucumber, SpecFlow, or Behave.

4. What is the main difference between BDD and TDD? BDD describes behavior from a business perspective; TDD focuses on technical units.

5. What is an advantage of BDD? Business and development teams share a common understanding of requirements.

Key Resources

1. https://cucumber.io/docs/bdd/
2. https://specflow.org/bdd/
3. https://en.wikipedia.org/wiki/Behavior-driven_development

Continue on the Software Testing Learning Path

The next article in the Software Testing learning path covers Test Automation and Software Quality — how test automation improves software quality.