Af Bdd Expertise

BDD Expertise

When to Use This Skill

Load this skill when you need to:

• Transform requirements into Markdown scenario specifications
• Write BDD scenarios with complete coverage
• Enforce glossary compliance in scenarios
• Design test coverage strategy
• Review scenario quality and completeness
• Understand Preconditions/Steps/Expected patterns

Common triggers:

• Refinement phase creates scenario specifications
• BDD-agent invoked by orchestrator
• Reviewing scenario coverage
• Adding new test scenarios
• Validating glossary compliance

Quick Reference

BDD (Behavior-Driven Development) transforms requirements into executable specifications using domain language, comprehensive scenario coverage, and strict glossary compliance.

Key principles:

• Write in domain language (from glossary), not UI language or implementation details
• Classify scenarios by test type: E2E, Integration, Component, or Unit
• Scenarios are Markdown specifications that AI converts to tests
• Scenario → Test is direct (no intermediate Gherkin layer)

Coverage requirements: Every feature needs happy path, error, boundary, and validation scenarios.

Test type classification (MUST specify for each scenario):

Output location:

docs/requirements/mini-prd/[feature-name].md
├── Section 4: Scenarios       ← Markdown scenario specs
└── Section 5: Visual Specs    ← Storybook + RTL tests + Selector contract

Scenarios Feed Test Generation

Scenarios written here become executable tests in Delivery phase:

Refinement phase (YOU ARE HERE):
  Write Markdown scenarios ──────────────────┐
  Define selector contract ──────────────────┤
                                             │
Delivery Phase (RED):                        │
  AI generates test files FROM scenarios: ◄──┘
    - E2E scenarios → Playwright specs
    - Integration scenarios → Jest tests
    - Component scenarios → RTL tests (often created in Refinement by ux-design-agent)
    - Unit scenarios → Jest tests

Your job: Write clear, complete scenarios with test type tags. AI handles conversion to executable tests.

See Testing Expertise for test writing timeline details.

Rules

Critical BDD Rules

1. Always check glossary BEFORE writing scenarios - Use approved terms only
2. Every scenario set MUST link to Linear issue - Reference in mini-PRD header
3. Every scenario MUST have test type - E2E, Integration, Component, or Unit
4. Every scenario MUST have coverage category - Happy, Error, Boundary, or Validation
5. Minimum scenario coverage - At least 1 happy path, 1 error case per feature
6. Use domain language, not UI language - "apply promo_code" not "click Submit button"
7. No implementation details - Behaviors only, not database/API calls
8. Explicit actors always - "the customer" not passive voice
9. Measurable outcomes only - Specific values, not "works correctly"
10. Replace synonyms with approved terms - Check glossary for exact wording
11. Reference selector contract - E2E and Component scenarios reference selectors

Scenario Structure Rules

12. Use Preconditions/Steps/Expected format - Not Given/When/Then
13. Scenarios live in mini-PRD Section 4 - Not separate .feature files
14. Scenarios reference selector contract - For testable UI elements
15. Scenario names use sentence case - "User signs up with valid email"
16. Group scenarios by test type - E2E first, then Integration, Component, Unit

Quality Rules

17. Keep scenarios focused - One behavior per scenario
18. Keep scenarios concise - Under 10 items in Steps section
19. Specific error messages - Include exact wording in Expected section
20. Use tables for data-driven scenarios - When testing same behavior with different data

Workflows

Workflow: Creating Scenarios from Refinement

When: Refinement phase, transforming Linear issue into executable specification

Procedure:

1. Read glossary file
   Location: /docs/glossary.yml or .claude/templates/glossary.yml
   Check all approved terms, synonyms, forbidden terms

2. Extract Linear issue details
   - Issue ID for reference in mini-PRD
   - Acceptance criteria as scenario seeds
   - User stories for actor identification

3. Identify scenarios from acceptance criteria
   For each acceptance criterion:
   - What's the happy path?
   - What errors could occur?
   - What edge cases exist?
   - What validation is needed?

4. Classify each scenario by test type
   Ask for each scenario:
   - Does it require real UI + real backend? → E2E
   - Does it test backend/API without UI? → Integration
   - Does it test component behavior? → Component
   - Does it test pure logic? → Unit

5. Write scenarios in Markdown format
   For each scenario:
   - Test Type label
   - Selector contract reference (if UI involved)
   - Preconditions (initial state)
   - Steps (user/system actions)
   - Expected (verifiable outcomes)

6. Review for glossary compliance
   - All terms match approved glossary
   - No synonyms used
   - No forbidden terms present

7. Verify coverage completeness
   - At least 1 happy path
   - Relevant error cases
   - Boundary conditions where applicable
   - Input validation where applicable

Workflow: Enforcing Glossary Compliance

When: Writing or reviewing any BDD scenario

Procedure:

1. Load glossary file
   .claude/templates/glossary.yml or /docs/glossary.yml

2. Identify all domain terms in scenario
   - Nouns (customer, order, promo_code)
   - Verbs (apply, submit, cancel)
   - States (active, expired, pending)

3. Check each term against glossary
   For each term:
   - Is it an approved term? → Use exactly as defined
   - Is it a synonym? → Replace with approved term
   - Is it forbidden? → Must replace
   - Is it missing? → Request glossary update

4. Apply replacements
   Examples:
   - "shopper" → "customer" (synonym)
   - "voucher" → "promo_code" (forbidden)
   - "discount code" → "promo_code" (synonym)

5. Verify snake_case for compound terms
   - promo_code (not promoCode or promo-code)
   - order_total (not orderTotal)
   - Apply consistently across all scenarios

Workflow: Classifying Scenarios by Test Type

When: Writing scenarios, deciding which test type each belongs to

Procedure:

1. Ask: Is this a complete user journey through real UI + real backend?
   - YES → E2E (Playwright)
   - NO → Continue to step 2

2. Ask: Does this test backend/API behavior without UI?
   - YES → Integration (Jest + SDK)
   - NO → Continue to step 3

3. Ask: Does this test component behavior and user interaction?
   - YES → Component (RTL)
   - NO → Continue to step 4

4. It's pure logic/validation
   → Unit (Jest isolated)

Decision matrix:
┌────────────────────────────────────┬─────────────────┐
│ Scenario Type                      │ Test Type       │
├────────────────────────────────────┼─────────────────┤
│ User completes multi-page journey  │ E2E             │
│ Full signup → verify → dashboard   │ E2E             │
│ Cross-page navigation flow         │ E2E             │
├────────────────────────────────────┼─────────────────┤
│ JWT contains correct claims        │ Integration     │
│ Lambda creates tenant record       │ Integration     │
│ API returns correct error code     │ Integration     │
│ Cross-tenant access blocked        │ Integration     │
├────────────────────────────────────┼─────────────────┤
│ Button disables during submission  │ Component       │
│ Form shows validation errors       │ Component       │
│ Loading state displays correctly   │ Component       │
│ Accessible roles are correct       │ Component       │
├────────────────────────────────────┼─────────────────┤
│ Email format validation logic      │ Unit            │
│ Password strength calculation      │ Unit            │
│ Price discount calculation         │ Unit            │
│ Date formatting function           │ Unit            │
└────────────────────────────────────┴─────────────────┘

Workflow: Reviewing Scenario Coverage

When: Before approving Refinement phase, during quality checks

Procedure:

1. Check mini-PRD structure
   ✅ Section 4 contains scenarios
   ✅ Section 5 contains selector contract
   ✅ Links to Linear issue present

2. Check scenario coverage
   ✅ At least 1 happy path scenario
   ✅ At least 1 error scenario
   ✅ Relevant boundary scenarios (limits, edges)
   ✅ Relevant validation scenarios (input checking)

3. Check test type distribution
   Guideline (not strict enforcement):
   - Unit: ~50% of scenarios
   - Component: ~20% of scenarios
   - Integration: ~20% of scenarios
   - E2E: ~10% of scenarios

   Flag unusual distributions for discussion, but don't block.

4. Review scenario quality
   Each scenario:
   ✅ Uses domain language (not UI language)
   ✅ No implementation details leaked
   ✅ Clear actor identification
   ✅ Measurable, specific outcomes
   ✅ References selector contract (if UI involved)

5. Verify glossary compliance
   ✅ All domain terms match glossary
   ✅ No synonyms used
   ✅ No forbidden terms present
   ✅ Consistent snake_case for compound terms

6. Check acceptance criteria coverage
   For each Linear acceptance criterion:
   ✅ Mapped to at least one scenario
   ✅ Happy path tested
   ✅ Error cases considered

Scenario Format

Markdown Scenario Structure

## Scenarios

### E2E: User signs up with valid email
**Test Type:** E2E (complete user journey)
**Selectors:** AUTH.signup.*

**Preconditions:**
- User is not logged in
- Email address not already registered

**Steps:**
1. User navigates to /signup
2. User enters valid email and strong password
3. User submits form

**Expected:**
- Verification email sent
- User sees "Check your email" message
- User record created in Cognito (unverified)

---

### Component: Signup form disables submit when password weak
**Test Type:** Component (RTL)
**Selectors:** AUTH.signup.*

**Preconditions:**
- SignupForm component rendered
- Email field has valid email

**Steps:**
1. User types weak password (e.g., "weak")

**Expected:**
- Submit button is disabled
- Password error message visible: "Password is too short"
- Error has accessible role

---

### Unit: Password validation rules
**Test Type:** Unit (pure logic)

**Test cases:**
| Input | Expected Result |
|-------|-----------------|
| "weak" | { valid: false, errors: ["Too short", "No uppercase", "No number"] } |
| "WeakPass1" | { valid: true, errors: [] } |
| "nouppercaseornumber" | { valid: false, errors: ["No uppercase", "No number"] } |

Selector Contract Reference

Scenarios that test UI elements must reference the selector contract:

**Selectors:** AUTH.signup.*

The selector contract is defined in Section 5 of the mini-PRD and implemented in /tests/selectors/[capability].ts:

// tests/selectors/auth.ts
export const AUTH = {
  signup: {
    form: 'signup-form',
    email: 'signup-email',
    password: 'signup-password',
    submit: 'signup-submit',
    successMessage: 'signup-success',
    passwordError: 'signup-password-error',
  },
};

Examples

Good: Domain Language (Not UI Language)

✅ Correct - Domain-focused:

### E2E: Apply valid promo_code at checkout
**Test Type:** E2E
**Selectors:** CHECKOUT.promo.*

**Preconditions:**
- Customer is signed in
- Cart contains items totaling $100
- Active promo_code "SAVE10" exists with 10% discount

**Steps:**
1. Customer navigates to checkout
2. Customer applies promo_code "SAVE10"

**Expected:**
- order_total reduced to $90
- Success message: "Promo code applied successfully"

❌ Wrong - UI-focused:

### Test: Click apply button with code

**Steps:**
1. I'm on the checkout page
2. I type "SAVE10" in the promo code text box
3. I click the green "Apply" button

**Expected:**
- The total field shows $90
- A green success banner appears

Why wrong: Describes UI interactions instead of business behavior.

Good: No Implementation Details

✅ Correct - Behavior-focused:

### Integration: Customer receives order confirmation
**Test Type:** Integration

**Preconditions:**
- Customer has completed checkout
- Payment processed successfully

**Steps:**
1. System processes payment completion

**Expected:**
- Confirmation email sent within 30 seconds
- Order status is "confirmed"
- Order appears in customer's order history

❌ Wrong - Implementation leaked:

### Test: Send email after payment

**Steps:**
1. Row exists in orders table with status='pending'
2. POST /api/payments returns 200 OK

**Expected:**
- INSERT into email_queue with template_id=5
- UPDATE orders SET status='confirmed' WHERE id=123

Why wrong: Exposes database, API, and technical implementation.

Good: Glossary Compliance

✅ Correct - Approved terms:

**Preconditions:**
- The customer has an active promo_code

**Steps:**
1. Customer applies the promo_code at checkout

**Expected:**
- order_total reflects the discount

❌ Wrong - Synonyms and forbidden terms:

**Preconditions:**
- The shopper has a valid voucher

**Steps:**
1. User enters the coupon code

**Expected:**
- Cart total is updated

Why wrong: Uses "shopper" (synonym), "voucher" (forbidden), "user" (synonym), "coupon" (forbidden), "cart" (should be "order" at checkout).

Good: Complete Coverage Set

✅ Correct - Comprehensive:

### E2E: Successfully apply valid promo_code
**Test Type:** E2E
...happy path...

### E2E: Reject expired promo_code
**Test Type:** E2E
...expiration error...

### Integration: Reject already-used single-use promo_code
**Test Type:** Integration
...usage limit error...

### Integration: Promo_code with minimum order - just under
**Test Type:** Integration
...boundary case below minimum...

### Component: Promo input shows format error
**Test Type:** Component
...format validation...

### Unit: Promo_code format validation
**Test Type:** Unit
| Input | Expected |
|-------|----------|
| "SAVE10" | valid |
| "save-10" | invalid (lowercase, hyphen) |
| "" | invalid (empty) |

❌ Wrong - Only happy path:

### E2E: Apply promo code
...only tests success case...

# Missing: error scenarios, boundaries, validation

Why wrong: Incomplete coverage leads to bugs in production.

Good: Component Scenario with RTL Focus

✅ Correct - Behavior and accessibility focused:

### Component: Password field shows strength indicator
**Test Type:** Component (RTL)
**Selectors:** AUTH.signup.*

**Preconditions:**
- SignupForm component rendered
- Password field is empty

**Steps:**
1. User types "weak" in password field
2. User continues typing to "WeakPass1"

**Expected (after step 1):**
- Strength indicator shows "Weak"
- Indicator has aria-label "Password strength: weak"
- Submit button is disabled

**Expected (after step 2):**
- Strength indicator shows "Strong"
- Indicator has aria-label "Password strength: strong"
- Submit button is enabled

Common Pitfalls

1. Skipping Glossary Check

Problem: Writing scenarios without consulting glossary first

Impact: Inconsistent terminology, rework required

Solution: Always read glossary BEFORE writing scenarios

2. Using UI Language

Problem: Describing button clicks instead of business actions

Impact: Scenarios break when UI changes, not reusable for API tests

Solution: Focus on "what" not "how" - business behavior, not UI mechanics

3. Leaking Implementation

Problem: Mentioning database, APIs, technical details in scenarios

Impact: Scenarios become brittle, hard to understand for non-technical stakeholders

Solution: Write for business audience - they shouldn't need to understand your tech stack

4. Vague Outcomes

Problem: "Then it works" or "User is happy"

Impact: Not testable, not measurable, not clear

Solution: Be specific - exact values, error messages, visible outcomes

5. Missing Test Type Classification

Problem: Scenarios without E2E/Integration/Component/Unit classification

Impact: No clear implementation path, all become slow E2E tests

Solution: Classify each scenario during writing - ask "What's the minimum test scope?"

6. All Scenarios as E2E

Problem: Everything classified as E2E

Impact: Slow test suite, brittle tests, expensive to maintain

Solution: Push tests down the pyramid - Unit for logic, Component for UI behavior, Integration for APIs, E2E only for critical journeys

7. Missing Selector Contract Reference

Problem: UI scenarios don't reference selector contract

Impact: Tests use arbitrary selectors, components don't have test IDs

Solution: Always specify which selector namespace scenarios use

8. Scenarios Too Long

Problem: 15+ steps in a single scenario

Impact: Hard to read, debug failures, maintain

Solution: Split into multiple focused scenarios, one behavior each

Test Type Distribution Guidelines

The test pyramid ratio is a guideline, not enforcement:

Agent behavior:

• Observe the distribution after scenarios are written
• Flag unusual distributions for discussion
• Ask questions if the ratio seems off
• Do NOT block progress based on ratio alone

Essential Reading

For testing implementation patterns:

• Testing Guide - Complete testing strategy, RTL patterns, E2E patterns

For glossary template and structure:

• Glossary Template - YAML format for approved terms

For selector contract patterns:

• Selector Contract Template - TypeScript selector structure

Remember:

1. Glossary compliance is mandatory, not optional
2. Domain language keeps scenarios stable as UI changes
3. Complete coverage (happy/error/boundary/validation) prevents bugs
4. Specific, measurable outcomes make scenarios testable
5. Test type classification determines implementation approach
6. Selector contracts bridge design and testing