spec-driven-development

# Spec-Driven Development

A comprehensive methodology for systematic software feature development that ensures quality, maintainability, and successful delivery through structured planning.

## When to Use This Skill

**Ideal scenarios:**
- Complex features with multiple components, integrations, or user interactions
- High-stakes projects where rework costs are significant
- Team collaboration requiring shared understanding
- AI-assisted development where clear structure improves output quality
- Knowledge preservation for future maintainers

**Less suitable:**
- Simple bug fixes with obvious solutions
- Experimental prototypes for rapid iteration
- Time-critical hotfixes requiring immediate action
- Well-established patterns with minimal ambiguity

## The Three-Phase Workflow

### Phase 1: Requirements Gathering

**Purpose:** Transform vague feature ideas into clear, testable requirements

**Process:**
1. Capture user stories expressing value and purpose
2. Define acceptance criteria using EARS format (Easy Approach to Requirements Syntax)
3. Identify edge cases and constraints
4. Validate completeness and feasibility

**EARS Format Patterns:**
```
WHEN [event] THEN [system] SHALL [response]
IF [precondition] THEN [system] SHALL [response]
WHEN [event] AND [condition] THEN [system] SHALL [response]
```

**Example:**
```markdown
**User Story:** As a new user, I want to create an account, so that I can access personalized features.

**Acceptance Criteria:**
1. WHEN user provides valid email and password THEN system SHALL create new account
2. WHEN user provides existing email THEN system SHALL display "email already registered" error
3. WHEN user provides password shorter than 8 characters THEN system SHALL display "password too short" error
4. WHEN account creation succeeds THEN system SHALL send confirmation email
```

### Phase 2: Design Documentation

**Purpose:** Create a comprehensive technical plan for implementation

**Process:**
1. Research technical appro