Phase 3: Develop Overview

Welcome to the Develop phase - where your carefully planned designs become working software! This phase focuses on AI-assisted development with human oversight, ensuring both rapid delivery and high quality through the "Vibe Coding" methodology.

Phase Objectives

By the end of the Develop phase, you will have:

✅ Production-Ready Code - Fully functional implementation following design specifications
✅ Comprehensive Test Suite - Unit, integration, and end-to-end tests with high coverage
✅ Quality Assurance - Code that meets standards for maintainability, security, and performance
✅ Documentation - Technical documentation and API references updated with implementation
✅ CI/CD Pipeline - Automated testing and deployment pipeline ready for production

Why the Develop Phase Matters

The Develop Phase Advantage:

• 3x faster development through AI acceleration with human oversight
• 60% fewer bugs due to systematic testing and quality gates
• 90% reduction in integration conflicts through continuous integration
• 50% less rework thanks to clear specifications from Design phase

The Vibe Coding Methodology

Vibe Coding is GISE's approach to AI-assisted development that maintains human control while leveraging AI acceleration:

Core Principles of Vibe Coding

1. Human in Command: Developer makes all strategic decisions
2. AI as Accelerator: AI handles routine coding tasks and boilerplate
3. Continuous Validation: Every AI output is reviewed and validated
4. Quality First: Automated quality gates prevent regressions
5. Iterative Refinement: Rapid feedback loops for continuous improvement

The Development Process

The Develop phase follows a structured workflow optimized for AI-assisted development:

1. Development Environment Setup (Day 1-2)

Prepare your development toolchain

• Configure AI-enhanced IDE (Cursor, VSCode with Copilot)
• Set up project structure following design specifications
• Configure linting, formatting, and quality tools
• Set up local development environment with containers

2. Feature Implementation Cycles (Day 3-14)

Implement features using Vibe Coding methodology

• Plan implementation approach for each feature
• Use AI assistance for code generation and boilerplate
• Implement comprehensive test coverage
• Conduct code reviews for quality assurance
• Continuous integration and testing

3. Quality Assurance (Day 15-16)

Ensure production readiness

• Run full test suite with coverage analysis
• Perform security scanning and vulnerability assessment
• Conduct performance testing and optimization
• Validate against design specifications

4. Documentation and Handoff (Day 17-18)

Prepare for deployment

• Generate and update technical documentation
• Create deployment and operational guides
• Conduct knowledge transfer sessions
• Prepare production deployment checklist

Key Development Deliverables

Production-Ready Codebase

Well-structured, maintainable code following best practices

// Example: Clean, well-structured TypeScript code
// src/services/ProjectService.ts

import { injectable, inject } from 'inversify';
import { ProjectRepository } from '../repositories/ProjectRepository';
import { UserService } from './UserService';
import { Project, CreateProjectDto, UpdateProjectDto } from '../types/Project';
import { ValidationError, NotFoundError, ForbiddenError } from '../errors';
import { Logger } from '../utils/Logger';

@injectable()
export class ProjectService {
  constructor(
    @inject('ProjectRepository') private projectRepository: ProjectRepository,
    @inject('UserService') private userService: UserService,
    @inject('Logger') private logger: Logger
  ) {}

  async createProject(userId: string, projectData: CreateProjectDto): Promise<Project> {
    this.logger.info('Creating new project', { userId, projectName: projectData.name });
    
    // Validate user exists and is active
    const user = await this.userService.findById(userId);
    if (!user) {
      throw new NotFoundError('User not found');
    }

    // Validate project data
    this.validateProjectData(projectData);

    // Check user permissions
    const canCreateProject = await this.userService.canCreateProject(userId);
    if (!canCreateProject) {
      throw new ForbiddenError('User cannot create projects');
    }

    try {
      const project = await this.projectRepository.create({
        ...projectData,
        ownerId: userId,
        status: 'draft',
        createdAt: new Date(),
        updatedAt: new Date()
      });

      this.logger.info('Project created successfully', { 
        projectId: project.id, 
        userId,
        projectName: project.name 
      });

      return project;
    } catch (error) {
      this.logger.error('Failed to create project', { 
        error: error.message, 
        userId,
        projectData 
      });
      throw error;
    }
  }

  async updateProject(
    userId: string, 
    projectId: string, 
    updateData: UpdateProjectDto
  ): Promise<Project> {
    // Find existing project
    const existingProject = await this.projectRepository.findById(projectId);
    if (!existingProject) {
      throw new NotFoundError('Project not found');
    }

    // Check permissions
    const canEdit = await this.canEditProject(userId, projectId);
    if (!canEdit) {
      throw new ForbiddenError('User cannot edit this project');
    }

    // Validate update data
    this.validateUpdateData(updateData);

    // Apply updates
    const updatedProject = await this.projectRepository.update(projectId, {
      ...updateData,
      updatedAt: new Date()
    });

    this.logger.info('Project updated', { projectId, userId, changes: updateData });

    return updatedProject;
  }

  private validateProjectData(data: CreateProjectDto): void {
    if (!data.name || data.name.trim().length === 0) {
      throw new ValidationError('Project name is required');
    }

    if (data.name.length > 255) {
      throw new ValidationError('Project name must be less than 255 characters');
    }

    if (data.description && data.description.length > 2000) {
      throw new ValidationError('Project description must be less than 2000 characters');
    }
  }

  private async canEditProject(userId: string, projectId: string): Promise<boolean> {
    const project = await this.projectRepository.findById(projectId);
    return project?.ownerId === userId || 
           await this.userService.hasPermission(userId, 'project:edit');
  }
}

Comprehensive Test Suite

Full test coverage with unit, integration, and end-to-end tests

// Example: Comprehensive test suite
// tests/services/ProjectService.test.ts

import { describe, beforeEach, afterEach, it, expect, jest } from '@jest/globals';
import { ProjectService } from '../../src/services/ProjectService';
import { ProjectRepository } from '../../src/repositories/ProjectRepository';
import { UserService } from '../../src/services/UserService';
import { Logger } from '../../src/utils/Logger';
import { ValidationError, NotFoundError, ForbiddenError } from '../../src/errors';
import { mockProject, mockUser, mockCreateProjectDto } from '../fixtures';

describe('ProjectService', () => {
  let projectService: ProjectService;
  let mockProjectRepository: jest.Mocked<ProjectRepository>;
  let mockUserService: jest.Mocked<UserService>;
  let mockLogger: jest.Mocked<Logger>;

  beforeEach(() => {
    mockProjectRepository = {
      create: jest.fn(),
      findById: jest.fn(),
      update: jest.fn(),
      delete: jest.fn(),
      findByUserId: jest.fn()
    } as jest.Mocked<ProjectRepository>;

    mockUserService = {
      findById: jest.fn(),
      canCreateProject: jest.fn(),
      hasPermission: jest.fn()
    } as jest.Mocked<UserService>;

    mockLogger = {
      info: jest.fn(),
      error: jest.fn(),
      warn: jest.fn(),
      debug: jest.fn()
    } as jest.Mocked<Logger>;

    projectService = new ProjectService(
      mockProjectRepository,
      mockUserService,
      mockLogger
    );
  });

  afterEach(() => {
    jest.clearAllMocks();
  });

  describe('createProject', () => {
    const userId = 'user-123';
    const projectData = mockCreateProjectDto();

    it('should create project successfully', async () => {
      // Arrange
      const mockUser = { id: userId, email: 'test@example.com', status: 'active' };
      const createdProject = mockProject({ ownerId: userId, name: projectData.name });

      mockUserService.findById.mockResolvedValue(mockUser);
      mockUserService.canCreateProject.mockResolvedValue(true);
      mockProjectRepository.create.mockResolvedValue(createdProject);

      // Act
      const result = await projectService.createProject(userId, projectData);

      // Assert
      expect(result).toEqual(createdProject);
      expect(mockProjectRepository.create).toHaveBeenCalledWith({
        ...projectData,
        ownerId: userId,
        status: 'draft',
        createdAt: expect.any(Date),
        updatedAt: expect.any(Date)
      });
      expect(mockLogger.info).toHaveBeenCalledWith(
        'Project created successfully',
        expect.objectContaining({ projectId: createdProject.id })
      );
    });

    it('should throw NotFoundError when user does not exist', async () => {
      // Arrange
      mockUserService.findById.mockResolvedValue(null);

      // Act & Assert
      await expect(projectService.createProject(userId, projectData))
        .rejects.toThrow(NotFoundError);
      
      expect(mockProjectRepository.create).not.toHaveBeenCalled();
    });

    it('should throw ForbiddenError when user cannot create projects', async () => {
      // Arrange
      const mockUser = { id: userId, email: 'test@example.com', status: 'active' };
      
      mockUserService.findById.mockResolvedValue(mockUser);
      mockUserService.canCreateProject.mockResolvedValue(false);

      // Act & Assert
      await expect(projectService.createProject(userId, projectData))
        .rejects.toThrow(ForbiddenError);
      
      expect(mockProjectRepository.create).not.toHaveBeenCalled();
    });

    it('should throw ValidationError for invalid project name', async () => {
      // Arrange
      const invalidProjectData = { ...projectData, name: '' };
      const mockUser = { id: userId, email: 'test@example.com', status: 'active' };
      
      mockUserService.findById.mockResolvedValue(mockUser);
      mockUserService.canCreateProject.mockResolvedValue(true);

      // Act & Assert
      await expect(projectService.createProject(userId, invalidProjectData))
        .rejects.toThrow(ValidationError);
      
      expect(mockProjectRepository.create).not.toHaveBeenCalled();
    });

    it('should log error when repository throws exception', async () => {
      // Arrange
      const mockUser = { id: userId, email: 'test@example.com', status: 'active' };
      const repositoryError = new Error('Database connection failed');
      
      mockUserService.findById.mockResolvedValue(mockUser);
      mockUserService.canCreateProject.mockResolvedValue(true);
      mockProjectRepository.create.mockRejectedValue(repositoryError);

      // Act & Assert
      await expect(projectService.createProject(userId, projectData))
        .rejects.toThrow(repositoryError);
      
      expect(mockLogger.error).toHaveBeenCalledWith(
        'Failed to create project',
        expect.objectContaining({ error: repositoryError.message })
      );
    });
  });

  describe('updateProject', () => {
    // Additional test cases for update functionality...
  });
});

Quality Assurance Configuration

Automated quality gates and monitoring

{
  "name": "project-management-api",
  "scripts": {
    "dev": "tsx watch src/server.ts",
    "build": "tsc && tsc-alias",
    "start": "node dist/server.js",
    "test": "jest",
    "test:watch": "jest --watch",
    "test:coverage": "jest --coverage",
    "test:integration": "jest --testPathPattern=integration",
    "test:e2e": "jest --testPathPattern=e2e",
    "lint": "eslint src --ext .ts,.tsx",
    "lint:fix": "eslint src --ext .ts,.tsx --fix",
    "format": "prettier --write src/**/*.{ts,tsx}",
    "format:check": "prettier --check src/**/*.{ts,tsx}",
    "type-check": "tsc --noEmit",
    "security": "audit-ci --config .audit-ci.json",
    "quality": "npm run lint && npm run type-check && npm run test:coverage && npm run security"
  },
  "devDependencies": {
    "@typescript-eslint/eslint-plugin": "^6.0.0",
    "@typescript-eslint/parser": "^6.0.0",
    "eslint": "^8.45.0",
    "eslint-config-prettier": "^8.8.0",
    "eslint-plugin-security": "^1.7.1",
    "jest": "^29.6.1",
    "prettier": "^3.0.0",
    "tsx": "^3.12.7",
    "typescript": "^5.1.6"
  }
}

ESLint Configuration:

// .eslintrc.js
module.exports = {
  parser: '@typescript-eslint/parser',
  parserOptions: {
    ecmaVersion: 2021,
    sourceType: 'module',
    project: './tsconfig.json'
  },
  plugins: ['@typescript-eslint', 'security'],
  extends: [
    'eslint:recommended',
    '@typescript-eslint/recommended',
    '@typescript-eslint/recommended-requiring-type-checking',
    'plugin:security/recommended',
    'prettier'
  ],
  rules: {
    // TypeScript specific rules
    '@typescript-eslint/no-unused-vars': 'error',
    '@typescript-eslint/explicit-function-return-type': 'warn',
    '@typescript-eslint/no-explicit-any': 'error',
    '@typescript-eslint/prefer-nullish-coalescing': 'error',
    '@typescript-eslint/prefer-optional-chain': 'error',
    
    // Security rules
    'security/detect-object-injection': 'error',
    'security/detect-non-literal-regexp': 'error',
    'security/detect-possible-timing-attacks': 'error',
    
    // Code quality rules
    'no-console': 'warn',
    'no-debugger': 'error',
    'prefer-const': 'error',
    'no-var': 'error',
    'eqeqeq': 'error',
    'curly': 'error'
  },
  env: {
    node: true,
    jest: true
  }
};

AI Integration in Development

AI-Assisted Code Generation

Recommended AI Tools for Development:

Tool	Best For	Integration	Strength
Cursor	Full development workflow	Native IDE	Complete project context
GitHub Copilot	Code completion and suggestions	VS Code, JetBrains	Real-time suggestions
ChatGPT/Claude	Complex problem solving	Browser/API	Detailed explanations
Codeium	Code generation and chat	Multiple IDEs	Free alternative

Vibe Coding Sessions

Structured approach to AI-assisted development:

Session Structure:

1. Preparation (5 min): Review requirements and design specifications
2. Context Setting (5 min): Provide AI with relevant context and constraints
3. Code Generation (15-20 min): Generate initial implementation with AI
4. Review & Refinement (10-15 min): Review, understand, and refine code
5. Test Creation (10-15 min): Generate and validate test cases
6. Quality Validation (5-10 min): Run quality gates and fix issues

Development Best Practices

Code Quality Standards

Maintainable Code Principles:

• Single Responsibility: Each function/class has one clear purpose
• Dependency Injection: Use IoC containers for testability
• Error Handling: Comprehensive error handling with proper types
• Type Safety: Strict TypeScript configuration with no any types
• Documentation: Clear comments and JSDoc for public APIs

Security Best Practices:

• Input Validation: Validate all inputs at boundaries
• SQL Injection Prevention: Use parameterized queries only
• Authentication: Implement proper JWT handling
• Authorization: Role-based access control throughout
• Secrets Management: Never hardcode secrets in code

Testing Strategy

Test Pyramid Implementation:

Testing Categories:

• Unit Tests: Individual functions and methods (90%+ coverage target)
• Integration Tests: Service interactions and database operations
• End-to-End Tests: Complete user workflows and API contracts
• Performance Tests: Load testing for critical endpoints
• Security Tests: Vulnerability scanning and penetration testing

Continuous Integration Pipeline

CI/CD Pipeline Structure:

# .github/workflows/ci.yml
name: CI/CD Pipeline

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main, develop]

jobs:
  quality-checks:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '18'
          cache: 'npm'
      
      - name: Install dependencies
        run: npm ci
      
      - name: Type checking
        run: npm run type-check
      
      - name: Linting
        run: npm run lint
      
      - name: Security audit
        run: npm run security
      
      - name: Format checking
        run: npm run format:check

  tests:
    runs-on: ubuntu-latest
    services:
      postgres:
        image: postgres:15
        env:
          POSTGRES_PASSWORD: test
        options: >-
          --health-cmd pg_isready
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5
        ports:
          - 5432:5432
    
    steps:
      - uses: actions/checkout@v4
      
      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '18'
          cache: 'npm'
      
      - name: Install dependencies
        run: npm ci
      
      - name: Run unit tests
        run: npm run test:coverage
      
      - name: Run integration tests
        run: npm run test:integration
        env:
          DATABASE_URL: postgresql://postgres:test@localhost:5432/test
      
      - name: Upload coverage reports
        uses: codecov/codecov-action@v3

  build:
    needs: [quality-checks, tests]
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '18'
          cache: 'npm'
      
      - name: Install dependencies
        run: npm ci
      
      - name: Build application
        run: npm run build
      
      - name: Build Docker image
        run: docker build -t app:${{ github.sha }} .

Common Development Challenges

Challenge 1: AI-Generated Code Quality

Problem: AI generates functional but suboptimal code

Solutions:

• Establish clear coding standards and communicate them to AI
• Always review and refactor AI-generated code
• Use AI for boilerplate, human expertise for architecture
• Implement automated quality gates to catch issues

Challenge 2: Test Coverage and Quality

Problem: Achieving comprehensive test coverage with AI assistance

Solutions:

• Generate test cases with AI, but validate logic manually
• Focus on testing business logic, not just code coverage
• Use mutation testing to validate test effectiveness
• Implement both positive and negative test scenarios

Challenge 3: Integration Complexity

Problem: Different components not working together smoothly

Solutions:

• Follow contract-first development with API specifications
• Implement integration tests early and often
• Use feature flags for gradual rollouts
• Maintain clear service boundaries and interfaces

Challenge 4: Performance Optimization

Problem: AI-generated code may not be performance-optimized

Solutions:

• Profile application performance regularly
• Optimize database queries and indexes
• Implement caching strategies appropriately
• Use performance testing in CI/CD pipeline

Moving to Deploy Phase

Handoff Checklist

Before moving to the Deploy phase, ensure you have:

Code Quality:

• All features implemented according to specifications
• 90%+ test coverage with comprehensive test suite
• All quality gates passing (linting, type checking, security)
• Code review completed by team members
• Documentation updated and current

Production Readiness:

• Performance testing completed and optimized
• Security scanning passed with no critical issues
• Error handling and logging implemented
• Configuration management set up for different environments
• Health checks and monitoring endpoints implemented

Integration:

• API contracts validated against specifications
• Database migrations tested and documented
• External service integrations working correctly
• CI/CD pipeline configured and tested
• Deployment artifacts created and validated

Deploy Phase Preparation

What the Deploy team needs from Develop:

1. Tested Application - Fully tested, production-ready code
2. Deployment Artifacts - Container images and configuration files
3. Documentation - Installation, configuration, and operational guides
4. Monitoring Setup - Health checks and observability configuration
5. Rollback Plan - Strategy for handling deployment issues

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Next Steps

Ready to Start Development?

Follow this sequence to master the Develop phase:

1. Vibe Coding - Learn AI-assisted development methodology
2. Testing Framework - Implement comprehensive testing
3. Code Quality - Establish quality assurance practices
4. Collaboration - Master team development workflows

Need Quick Reference?

Use the Develop Phase Recipes for ready-to-use patterns and code templates.

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Remember: The Develop phase is where great design meets great execution. Use AI to accelerate development while maintaining human oversight for quality and architectural decisions.