bdd-patterns

name	bdd-patterns
user-invocable	false
description	Use when applying Behavior-Driven Development patterns including Given-When-Then structure, feature files, and acceptance criteria. Use when writing BDD-style tests and specifications.
allowed-tools	["Bash","Read"]

BDD Patterns

Master Behavior-Driven Development patterns to write clear, business-readable specifications that drive implementation.

Given-When-Then Structure

The fundamental BDD pattern uses three parts:

• Given: The initial context or preconditions
• When: The action or event being tested
• Then: The expected outcome or result

Feature: User Authentication

  Scenario: Successful login with valid credentials
    Given a registered user with email "[e-mail]"
    And the user has password "secure123"
    When the user submits the login form with correct credentials
    Then the user should be redirected to the dashboard
    And a session should be created

Feature File Organization

Feature: Shopping Cart
  As a customer
  I want to manage items in my cart
  So that I can purchase products I'm interested in

  Background:
    Given I am logged in as a customer
    And the product catalog is available

  Scenario: Add item to empty cart
    Given my cart is empty
    When I add "Blue T-Shirt" to my cart
    Then my cart should contain 1 item
    And the cart total should be $29.99

  Scenario: Remove item from cart
    Given my cart contains "Blue T-Shirt"
    When I remove "Blue T-Shirt" from my cart
    Then my cart should be empty

Scenario Outlines for Data-Driven Tests

Scenario Outline: Password validation
  Given I am on the registration page
  When I enter password "<password>"
  Then I should see "<message>"

  Examples:
    | password    | message                        |
    | abc         | Password too short             |
    | abcdefgh    | Password needs a number        |
    | abcdefgh1   | Password accepted              |
    | abcdefgh1!  | Password accepted              |

Step Definition Patterns

# Ruby/Cucumber example
Given('a registered user with email {string}') do |email|
  @user = User.create!(email: email, password: 'password123')
end

When('the user submits the login form with correct credentials') do
  visit login_path
  fill_in 'Email', with: @user.email
  fill_in 'Password', with: 'password123'
  click_button 'Log In'
end

Then('the user should be redirected to the dashboard') do
  expect(page).to have_current_path(dashboard_path)
end

When to Use This Skill

Use bdd-patterns when you need to:

• Write acceptance tests that stakeholders can understand
• Define behavior before implementation
• Create living documentation from tests
• Bridge communication between developers and business
• Ensure features meet business requirements

Best Practices

• Write scenarios from the user's perspective
• Keep scenarios focused on single behaviors
• Use declarative language, not implementation details
• Reuse step definitions across scenarios
• Use Background for common setup steps
• Keep feature files organized by domain area

Common Pitfalls

• Writing scenarios that are too technical
• Coupling steps to specific UI implementations
• Creating overly complex scenario outlines
• Not maintaining feature files as code changes
• Mixing multiple behaviors in one scenario