README.md

@@ -155,47 +155,16 @@ To backup your data:
 cp tablets.db tablets_backup_$(date +%Y%m%d).db
 ```
 
-## Testing
+## Version Control
 
-The project includes a comprehensive unit test suite with **46 tests** covering core functionality and edge cases.
-
-### Running Tests
-
-```bash
-# Install test dependencies (if not already installed)
-source .venv/bin/activate
-uv pip install pytest pytest-cov
-
-# Run all tests
-python3 -m pytest tests/ -v
-
-# Run with coverage report
-python3 -m pytest tests/ --cov=./ --cov-report=term-missing
-```
-
-### Test Structure
-
-| File | Tests | Coverage |
-|------|-------|----------|
-| `tests/test_core.py` | 21 | Core operations (tablet, user, loan CRUD) |
-| `tests/test_edge_cases.py` | 14 | Edge cases (duplicates, invalid IDs, etc.) |
-| `tests/test_minimal_app.py` | 11 | Application function tests |
-
-### Key Edge Cases Covered
-
-- Loan a device that's already loaned (prevents double-loaning)
-- Return a non-existent loan (handles gracefully)
-- Duplicate serial numbers (rejected at database level)
-- Duplicate user identifications (rejected at database level)
-- Invalid tablet/user IDs (validated before operations)
-- Multiple loans per user (one-to-many relationship)
-- Loan-return-loan sequence (device lifecycle)
-
-### Test Configuration
-
-Tests use isolated temporary databases and automatically clean up after each test run. No impact on production data.
+This project uses Git for version control with the following structure:
 
+- `master` - Production-ready releases
+- `develop` - Integration branch for features
+- `feature/*` - Individual feature branches
+- `hotfix/*` - Urgent bug fixes
 
+See `CONTRIBUTING.md` for detailed workflow and commit conventions.
 
 ## License
 

RUNNING.md

@@ -48,22 +48,10 @@ pkill -f "python app.py"
 - **Port**: 5000 (configurable in app.py)
 - **Virtual Environment**: `.venv/` (created with uv)
 
-## Running Tests
+## Troubleshooting
+If you have issues:
+1. Check if the server is running: `ps aux | grep app.py`
+2. Check the database: `sqlite3 tablets.db`
+3. Restart the server: `source .venv/bin/activate && python app.py`
 
-The project includes 46 unit tests for verifying functionality:
-
-```bash
-# Run all tests
-python3 -m pytest tests/ -v
-
-# Run with coverage
-python3 -m pytest tests/ --cov=./ --cov-report=term-missing
-```
-
-Tests cover:
-- Core CRUD operations for tablets, users, and loans
-- Edge cases (duplicates, invalid IDs, already loaned devices)
-- Application function testing
-- Non-loanable device management
-
-All tests use isolated temporary databases and do not affect production data.
+Enjoy managing your tablets! 📱💻

TECHNICAL_SPECIFICATIONS.md

@@ -147,54 +147,3 @@ def loan_device(device_id: int, user_id: int) -> Loan:
 - **Logging**: Registrar préstamos/devoluciones para auditoría
 - **Versionado API**: `/api/v1/...` para compatibilidad futura
 - **Pruebas**: Cubrir flujos críticos (préstamo con dispositivo no disponible, devolución de préstamo inexistente)
-
----
-
-## 9. Migración a PostgreSQL (Futuro)
-
-### Contexto
-
-El sistema actualmente utiliza **SQLite** como base de datos embebida, ideal para prototipos y aplicaciones pequeñas. Sin embargo, SQLite tiene limitaciones para escalar.
-
-### Criterios para Migración
-
-Considerar migrar a **PostgreSQL** cuando:
-- Tamaño DB > 1GB
-- Más de 50 conexiones simultáneas
-- Más de 200 usuarios activos
-- Más de 500 transacciones por minuto
-- Necesidad de múltiples servidores
-
-### Arquitectura Propuesta
-
-Usar un patrón de **Repository** para abstraer la base de datos:
-```
-backend/
-├── repositories/
-│   ├── base_repository.py       # Interfaz abstracta
-│   ├── sqlite_repository.py     # Implementación SQLite
-│   └── postgres_repository.py   # Implementación PostgreSQL
-└── config/
-    └── database.py              # Fábrica de repositorios
-```
-
-### Schema PostgreSQL
-
-El schema es similar al de SQLite pero con tipos de datos más específicos y índices adicionales para rendimiento.
-
-### Pasos para Migración
-
-1. Instalar dependencias: `pip install psycopg2-binary sqlalchemy alembic`
-2. Configurar PostgreSQL y crear base de datos
-3. Ejecutar script de migración: `python scripts/migrate_to_postgres.py`
-4. Cambiar configuración: `DB_TYPE=postgres`
-5. Iniciar aplicación
-
-### Beneficios
-
-- Concurrencia ilimitada (múltiples escritores)
-- Escalabilidad a miles de conexiones
-- Mejor rendimiento con índices
-- Seguridad integrada (autenticación, roles)
-- Backups automáticos
-- Replicación y clustering

docs/MIGRATION_TO_POSTGRES.md

@@ -1,987 +0,0 @@
-# PostgreSQL Migration Guide
-
-This document describes how to migrate the Tablet Management System from SQLite to PostgreSQL when the database grows beyond SQLite's capabilities.
-
-## When to Migrate
-
-Consider migrating to PostgreSQL when you encounter any of these scenarios:
-
-| Metric | SQLite Limit | PostgreSQL | Migration Trigger |
-|--------|--------------|------------|-------------------|
-| Database Size | ~10GB max | Unlimited | >1GB |
-| Concurrent Writers | 1 | Thousands | >50 simultaneous |
-| Active Users | <100 | Millions | >200 |
-| Transactions/min | <100 | 100K+ | >500 |
-| Servers | Single machine | Cluster | Multiple servers |
-| High Availability | No | Yes | Required |
-| Backup Strategy | Manual | Automated | Automated needed |
-
-## Architecture Overview
-
-The migration uses a **Repository Pattern** to abstract the database layer, allowing both SQLite and PostgreSQL to work seamlessly.
-
-```
-project/
-├── backend/
-│   ├── config/
-│   │   ├── __init__.py
-│   │   ├── settings.py          # Database configuration
-│   │   └── database.py          # Repository factory
-│   ├── repositories/
-│   │   ├── __init__.py
-│   │   ├── base_repository.py   # Abstract base classes
-│   │   ├── sqlite_repo.py       # SQLite implementation
-│   │   └── postgres_repo.py     # PostgreSQL implementation
-│   └── app.py                   # Main application (unchanged)
-├── migrations/                 # Alembic migrations
-│   └── versions/
-│       └── initial_schema.py
-├── scripts/
-│   └── migrate_to_postgres.py   # Migration script
-└── docker-compose.yml           # Optional Docker setup
-```
-
-## Step 1: Install Dependencies
-
-```bash
-# For development
-pip install psycopg2-binary sqlalchemy alembic
-
-# For production (more efficient)
-pip install psycopg2 sqlalchemy alembic
-```
-
-## Step 2: Set Up PostgreSQL
-
-### Option A: Local Installation
-
-```bash
-# Ubuntu/Debian
-sudo apt update
-sudo apt install postgresql postgresql-contrib
-
-# Create database and user
-sudo -u postgres psql
-```
-
-In PostgreSQL shell:
-```sql
-CREATE DATABASE tablet_management;
-CREATE USER tablet_user WITH PASSWORD 'your_secure_password';
-GRANT ALL PRIVILEGES ON DATABASE tablet_management TO tablet_user;
-ALTER USER tablet_user CREATEDB;
-\q
-```
-
-### Option B: Docker (Recommended for Development)
-
-```bash
-# Start PostgreSQL container
-docker run --name tablet-db -e POSTGRES_PASSWORD=your_password -e POSTGRES_USER=tablet_user -e POSTGRES_DB=tablet_management -p 5432:5432 -d postgres:16-alpine
-
-# Or use docker-compose (see docker-compose.yml)
-docker-compose up -d postgres
-```
-
-## Step 3: Configure Environment
-
-Create a `.env` file:
-
-```bash
-# Database configuration
-DB_TYPE=postgres                    # or 'sqlite'
-DB_URL=postgresql://tablet_user:your_password@localhost:5432/tablet_management
-
-# For SQLite (fallback)
-DB_PATH=tablets.db
-```
-
-Or set environment variables:
-
-```bash
-export DB_TYPE=postgres
-export DB_URL=postgresql://tablet_user:your_password@localhost:5432/tablet_management
-```
-
-## Step 4: Create Repository Abstraction
-
-### Base Repository (Abstract Interface)
-
-```python
-# backend/repositories/base_repository.py
-from abc import ABC, abstractmethod
-from typing import Optional, List
-from datetime import datetime
-
-
-class BaseTabletRepository(ABC):
-    @abstractmethod
-    def get_by_id(self, tablet_id: int) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_by_serial(self, serial: str) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_all(self, status: Optional[str] = None) -> List[dict]:
-        pass
-    
-    @abstractmethod
-    def add(self, brand: str, model: str, serial_number: str, notes: Optional[str] = None) -> dict:
-        pass
-    
-    @abstractmethod
-    def update_status(self, tablet_id: int, status: str) -> bool:
-        pass
-    
-    @abstractmethod
-    def delete(self, tablet_id: int) -> bool:
-        pass
-
-
-class BaseUserRepository(ABC):
-    @abstractmethod
-    def get_by_id(self, user_id: int) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_by_identification(self, identification: str) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_all(self) -> List[dict]:
-        pass
-    
-    @abstractmethod
-    def add(self, name: str, email: Optional[str], phone: Optional[str], identification: str) -> dict:
-        pass
-
-
-class BaseLoanRepository(ABC):
-    @abstractmethod
-    def get_by_id(self, loan_id: int) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_active_by_tablet(self, tablet_id: int) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_by_user(self, user_id: int) -> List[dict]:
-        pass
-    
-    @abstractmethod
-    def get_all(self, status: Optional[str] = None) -> List[dict]:
-        pass
-    
-    @abstractmethod
-    def create(self, tablet_id: int, user_id: int) -> dict:
-        pass
-    
-    @abstractmethod
-    def return_loan(self, loan_id: int) -> bool:
-        pass
-
-
-class BaseNonLoanableDeviceRepository(ABC):
-    @abstractmethod
-    def get_by_id(self, device_id: int) -> Optional[dict]:
-        pass
-    
-    @abstractmethod
-    def get_all(self) -> List[dict]:
-        pass
-    
-    @abstractmethod
-    def add(self, brand: str, model: str, serial_number: str, device_type: str, 
-            location: Optional[str] = None, notes: Optional[str] = None,
-            purchase_date: Optional[str] = None, purchase_cost: Optional[float] = None) -> dict:
-        pass
-    
-    @abstractmethod
-    def update(self, device_id: int, **kwargs) -> bool:
-        pass
-    
-    @abstractmethod
-    def delete(self, device_id: int) -> bool:
-        pass
-```
-
-### SQLite Implementation
-
-```python
-# backend/repositories/sqlite_repo.py
-import sqlite3
-from typing import Optional, List
-from .base_repository import (
-    BaseTabletRepository, BaseUserRepository, 
-    BaseLoanRepository, BaseNonLoanableDeviceRepository
-)
-
-
-class SQLiteTabletRepository(BaseTabletRepository):
-    def __init__(self, db_path: str = 'tablets.db'):
-        self.db_path = db_path
-        self._init_db()
-    
-    def _init_db(self):
-        conn = sqlite3.connect(self.db_path)
-        cursor = conn.cursor()
-        cursor.execute('''
-            CREATE TABLE IF NOT EXISTS tablets (
-                id INTEGER PRIMARY KEY AUTOINCREMENT,
-                brand TEXT NOT NULL,
-                model TEXT NOT NULL,
-                serial_number TEXT UNIQUE NOT NULL,
-                status TEXT DEFAULT 'available',
-                notes TEXT
-            )
-        ''')
-        conn.commit()
-        conn.close()
-    
-    def get_by_id(self, tablet_id: int) -> Optional[dict]:
-        conn = sqlite3.connect(self.db_path)
-        conn.row_factory = sqlite3.Row
-        cursor = conn.cursor()
-        cursor.execute("SELECT * FROM tablets WHERE id = ?", (tablet_id,))
-        row = cursor.fetchone()
-        conn.close()
-        return dict(row) if row else None
-    
-    def get_by_serial(self, serial: str) -> Optional[dict]:
-        conn = sqlite3.connect(self.db_path)
-        conn.row_factory = sqlite3.Row
-        cursor = conn.cursor()
-        cursor.execute("SELECT * FROM tablets WHERE serial_number = ?", (serial,))
-        row = cursor.fetchone()
-        conn.close()
-        return dict(row) if row else None
-    
-    def get_all(self, status: Optional[str] = None) -> List[dict]:
-        conn = sqlite3.connect(self.db_path)
-        conn.row_factory = sqlite3.Row
-        cursor = conn.cursor()
-        query = "SELECT * FROM tablets"
-        params = ()
-        if status:
-            query += " WHERE status = ?"
-            params = (status,)
-        cursor.execute(query, params)
-        results = [dict(row) for row in cursor.fetchall()]
-        conn.close()
-        return results
-    
-    def add(self, brand: str, model: str, serial_number: str, notes: Optional[str] = None) -> dict:
-        conn = sqlite3.connect(self.db_path)
-        conn.row_factory = sqlite3.Row
-        cursor = conn.cursor()
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status, notes)
-            VALUES (?, ?, ?, 'available', ?)
-        ''', (brand, model, serial_number, notes))
-        conn.commit()
-        tablet_id = cursor.lastrowid
-        cursor.execute("SELECT * FROM tablets WHERE id = ?", (tablet_id,))
-        row = cursor.fetchone()
-        conn.close()
-        return dict(row)
-    
-    def update_status(self, tablet_id: int, status: str) -> bool:
-        conn = sqlite3.connect(self.db_path)
-        cursor = conn.cursor()
-        cursor.execute("UPDATE tablets SET status = ? WHERE id = ?", (status, tablet_id))
-        conn.commit()
-        changed = cursor.rowcount > 0
-        conn.close()
-        return changed
-    
-    def delete(self, tablet_id: int) -> bool:
-        conn = sqlite3.connect(self.db_path)
-        cursor = conn.cursor()
-        cursor.execute("DELETE FROM tablets WHERE id = ?", (tablet_id,))
-        conn.commit()
-        deleted = cursor.rowcount > 0
-        conn.close()
-        return deleted
-
-
-# Similar implementations for SQLiteUserRepository, SQLiteLoanRepository, etc.
-```
-
-### PostgreSQL Implementation
-
-```python
-# backend/repositories/postgres_repo.py
-import psycopg2
-from psycopg2 import sql
-from psycopg2.extras import DictCursor
-from typing import Optional, List
-from .base_repository import (
-    BaseTabletRepository, BaseUserRepository,
-    BaseLoanRepository, BaseNonLoanableDeviceRepository
-)
-
-
-class PostgreSQLTabletRepository(BaseTabletRepository):
-    def __init__(self, connection_string: str):
-        self.connection_string = connection_string
-        self._init_db()
-    
-    def _get_connection(self):
-        return psycopg2.connect(self.connection_string)
-    
-    def _init_db(self):
-        conn = self._get_connection()
-        cursor = conn.cursor()
-        cursor.execute('''
-            CREATE TABLE IF NOT EXISTS tablets (
-                id SERIAL PRIMARY KEY,
-                brand VARCHAR(100) NOT NULL,
-                model VARCHAR(100) NOT NULL,
-                serial_number VARCHAR(50) UNIQUE NOT NULL,
-                status VARCHAR(20) DEFAULT 'available',
-                notes TEXT,
-                created_at TIMESTAMP DEFAULT NOW(),
-                updated_at TIMESTAMP DEFAULT NOW()
-            )
-        ''')
-        cursor.execute('''
-            CREATE INDEX IF NOT EXISTS idx_tablets_serial 
-            ON tablets(serial_number)
-        ''')
-        cursor.execute('''
-            CREATE INDEX IF NOT EXISTS idx_tablets_status 
-            ON tablets(status)
-        ''')
-        conn.commit()
-        cursor.close()
-        conn.close()
-    
-    def get_by_id(self, tablet_id: int) -> Optional[dict]:
-        conn = self._get_connection()
-        cursor = conn.cursor(cursor_factory=DictCursor)
-        cursor.execute("SELECT * FROM tablets WHERE id = %s", (tablet_id,))
-        row = cursor.fetchone()
-        conn.close()
-        return dict(row) if row else None
-    
-    def get_by_serial(self, serial: str) -> Optional[dict]:
-        conn = self._get_connection()
-        cursor = conn.cursor(cursor_factory=DictCursor)
-        cursor.execute("SELECT * FROM tablets WHERE serial_number = %s", (serial,))
-        row = cursor.fetchone()
-        conn.close()
-        return dict(row) if row else None
-    
-    def get_all(self, status: Optional[str] = None) -> List[dict]:
-        conn = self._get_connection()
-        cursor = conn.cursor(cursor_factory=DictCursor)
-        query = "SELECT * FROM tablets"
-        params = ()
-        if status:
-            query += " WHERE status = %s"
-            params = (status,)
-        cursor.execute(query, params)
-        results = [dict(row) for row in cursor.fetchall()]
-        conn.close()
-        return results
-    
-    def add(self, brand: str, model: str, serial_number: str, notes: Optional[str] = None) -> dict:
-        conn = self._get_connection()
-        cursor = conn.cursor(cursor_factory=DictCursor)
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status, notes)
-            VALUES (%s, %s, %s, 'available', %s)
-            RETURNING *
-        ''', (brand, model, serial_number, notes))
-        row = cursor.fetchone()
-        conn.commit()
-        conn.close()
-        return dict(row)
-    
-    def update_status(self, tablet_id: int, status: str) -> bool:
-        conn = self._get_connection()
-        cursor = conn.cursor()
-        cursor.execute(
-            "UPDATE tablets SET status = %s, updated_at = NOW() WHERE id = %s",
-            (status, tablet_id)
-        )
-        conn.commit()
-        changed = cursor.rowcount > 0
-        conn.close()
-        return changed
-    
-    def delete(self, tablet_id: int) -> bool:
-        conn = self._get_connection()
-        cursor = conn.cursor()
-        cursor.execute("DELETE FROM tablets WHERE id = %s", (tablet_id,))
-        conn.commit()
-        deleted = cursor.rowcount > 0
-        conn.close()
-        return deleted
-
-
-# Similar implementations for PostgreSQLUserRepository, PostgreSQLLoanRepository, etc.
-```
-
-## Step 5: Create Repository Factory
-
-```python
-# backend/config/database.py
-import os
-from backend.repositories.sqlite_repo import (
-    SQLiteTabletRepository, SQLiteUserRepository,
-    SQLiteLoanRepository, SQLiteNonLoanableDeviceRepository
-)
-from backend.repositories.postgres_repo import (
-    PostgreSQLTabletRepository, PostgreSQLUserRepository,
-    PostgreSQLLoanRepository, PostgreSQLNonLoanableDeviceRepository
-)
-from backend.repositories.base_repository import (
-    BaseTabletRepository, BaseUserRepository,
-    BaseLoanRepository, BaseNonLoanableDeviceRepository
-)
-
-
-class DatabaseConfig:
-    def __init__(self):
-        self.db_type = os.getenv('DB_TYPE', 'sqlite')
-        self.db_url = os.getenv('DB_URL', '')
-        self.db_path = os.getenv('DB_PATH', 'tablets.db')
-    
-    @property
-    def is_postgres(self) -> bool:
-        return self.db_type == 'postgres'
-
-
-def get_tablet_repository() -> BaseTabletRepository:
-    config = DatabaseConfig()
-    if config.is_postgres:
-        return PostgreSQLTabletRepository(config.db_url)
-    else:
-        return SQLiteTabletRepository(config.db_path)
-
-
-def get_user_repository() -> BaseUserRepository:
-    config = DatabaseConfig()
-    if config.is_postgres:
-        return PostgreSQLUserRepository(config.db_url)
-    else:
-        return SQLiteUserRepository(config.db_path)
-
-
-def get_loan_repository() -> BaseLoanRepository:
-    config = DatabaseConfig()
-    if config.is_postgres:
-        return PostgreSQLLoanRepository(config.db_url)
-    else:
-        return SQLiteLoanRepository(config.db_path)
-
-
-def get_non_loanable_device_repository() -> BaseNonLoanableDeviceRepository:
-    config = DatabaseConfig()
-    if config.is_postgres:
-        return PostgreSQLNonLoanableDeviceRepository(config.db_url)
-    else:
-        return SQLiteNonLoanableDeviceRepository(config.db_path)
-```
-
-## Step 6: Update Application to Use Repositories
-
-Modify your application to use the repository pattern:
-
-```python
-# In your app.py or service layer
-from backend.config.database import (
-    get_tablet_repository, get_user_repository,
-    get_loan_repository, get_non_loanable_device_repository
-)
-
-# Instead of direct SQLite calls:
-tablet_repo = get_tablet_repository()
-user_repo = get_user_repository()
-loan_repo = get_loan_repository()
-
-# Example: Loan a tablet
-def loan_tablet(tablet_id: int, user_id: int):
-    # Get repositories
-    tablet_repo = get_tablet_repository()
-    user_repo = get_user_repository()
-    loan_repo = get_loan_repository()
-    
-    # Validate
-    tablet = tablet_repo.get_by_id(tablet_id)
-    if not tablet:
-        raise ValueError("Tablet not found")
-    
-    if tablet['status'] != 'available':
-        raise ValueError("Tablet not available")
-    
-    user = user_repo.get_by_id(user_id)
-    if not user:
-        raise ValueError("User not found")
-    
-    # Check for active loan
-    active_loan = loan_repo.get_active_by_tablet(tablet_id)
-    if active_loan:
-        raise ValueError("Tablet already loaned")
-    
-    # Create loan
-    loan = loan_repo.create(tablet_id, user_id)
-    
-    # Update tablet status
-    tablet_repo.update_status(tablet_id, 'loaned')
-    
-    return loan
-```
-
-## Step 7: Create Migration Script
-
-```python
-# scripts/migrate_to_postgres.py
-#!/usr/bin/env python3
-"""
-Migration script from SQLite to PostgreSQL
-"""
-import sqlite3
-import psycopg2
-from psycopg2.extras import DictCursor
-import argparse
-from tqdm import tqdm
-import os
-
-
-def create_postgres_tables(conn):
-    """Create all tables in PostgreSQL"""
-    cursor = conn.cursor()
-    
-    # Tablets
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS tablets (
-            id SERIAL PRIMARY KEY,
-            brand VARCHAR(100) NOT NULL,
-            model VARCHAR(100) NOT NULL,
-            serial_number VARCHAR(50) UNIQUE NOT NULL,
-            status VARCHAR(20) DEFAULT 'available',
-            notes TEXT,
-            created_at TIMESTAMP DEFAULT NOW(),
-            updated_at TIMESTAMP DEFAULT NOW()
-        )
-    ''')
-    
-    # Users
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS users (
-            id SERIAL PRIMARY KEY,
-            name VARCHAR(100) NOT NULL,
-            email VARCHAR(255),
-            phone VARCHAR(20),
-            identification VARCHAR(50) UNIQUE NOT NULL,
-            created_at TIMESTAMP DEFAULT NOW(),
-            updated_at TIMESTAMP DEFAULT NOW()
-        )
-    ''')
-    
-    # Loans
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS loans (
-            id SERIAL PRIMARY KEY,
-            tablet_id INTEGER NOT NULL REFERENCES tablets(id) ON DELETE RESTRICT,
-            user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
-            loan_date TIMESTAMP NOT NULL DEFAULT NOW(),
-            return_date TIMESTAMP,
-            status VARCHAR(20) DEFAULT 'active',
-            created_at TIMESTAMP DEFAULT NOW()
-        )
-    ''')
-    
-    # Non-loanable devices
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS non_loanable_devices (
-            id SERIAL PRIMARY KEY,
-            brand VARCHAR(100) NOT NULL,
-            model VARCHAR(100) NOT NULL,
-            serial_number VARCHAR(50) UNIQUE NOT NULL,
-            device_type VARCHAR(50) NOT NULL,
-            location VARCHAR(100),
-            status VARCHAR(20) DEFAULT 'available',
-            notes TEXT,
-            purchase_date DATE,
-            purchase_cost DECIMAL(10,2),
-            created_at TIMESTAMP DEFAULT NOW(),
-            updated_at TIMESTAMP DEFAULT NOW()
-        )
-    ''')
-    
-    # Indexes for performance
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_tablets_serial ON tablets(serial_number)')
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_tablets_status ON tablets(status)')
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_tablets_brand ON tablets(brand)')
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_users_identification ON users(identification)')
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_loans_tablet ON loans(tablet_id)')
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_loans_user ON loans(user_id)')
-    cursor.execute('CREATE INDEX IF NOT EXISTS idx_loans_status ON loans(status)')
-    
-    conn.commit()
-
-
-def migrate_table(conn_sqlite, conn_pg, table_name: str, pg_create_table: str):
-    """Generic migration for a table"""
-    cursor_sqlite = conn_sqlite.cursor()
-    cursor_pg = conn_pg.cursor()
-    
-    # Get all data from SQLite
-    cursor_sqlite.execute(f"SELECT * FROM {table_name}")
-    rows = cursor_sqlite.fetchall()
-    
-    if not rows:
-        print(f"No data to migrate for {table_name}")
-        return
-    
-    # Get column names
-    column_names = [desc[0] for desc in cursor_sqlite.description]
-    
-    # Prepare INSERT statement
-    columns = ', '.join(column_names)
-    placeholders = ', '.join(['%s'] * len(column_names))
-    insert_sql = f"INSERT INTO {table_name} ({columns}) VALUES ({placeholders}) ON CONFLICT DO NOTHING"
-    
-    # Migrate data
-    for row in tqdm(rows, desc=f"Migrating {table_name}"):
-        cursor_pg.execute(insert_sql, row)
-    
-    conn_pg.commit()
-    print(f"✓ Migrated {len(rows)} rows from {table_name}")
-
-
-def migrate_all(sqlite_path: str, pg_url: str):
-    """Migrate all data from SQLite to PostgreSQL"""
-    print("Starting migration from SQLite to PostgreSQL...")
-    
-    # Connect to SQLite
-    conn_sqlite = sqlite3.connect(sqlite_path)
-    
-    # Connect to PostgreSQL
-    conn_pg = psycopg2.connect(pg_url)
-    
-    try:
-        # Create tables
-        print("Creating PostgreSQL tables...")
-        create_postgres_tables(conn_pg)
-        
-        # Migrate each table
-        migrate_table(conn_sqlite, conn_pg, 'tablets', '')
-        migrate_table(conn_sqlite, conn_pg, 'users', '')
-        migrate_table(conn_sqlite, conn_pg, 'loans', '')
-        migrate_table(conn_sqlite, conn_pg, 'non_loanable_devices', '')
-        
-        print("\n✓ Migration completed successfully!")
-        print(f"  SQLite: {sqlite_path}")
-        print(f"  PostgreSQL: {pg_url}")
-        
-    except Exception as e:
-        conn_pg.rollback()
-        print(f"\n✗ Migration failed: {e}")
-        raise
-    finally:
-        conn_sqlite.close()
-        conn_pg.close()
-
-
-if __name__ == '__main__':
-    parser = argparse.ArgumentParser(description='Migrate from SQLite to PostgreSQL')
-    parser.add_argument('--sqlite', default='tablets.db', help='SQLite database path')
-    parser.add_argument('--postgres', required=True, help='PostgreSQL connection URL')
-    args = parser.parse_args()
-    
-    migrate_all(args.sqlite, args.postgres)
-```
-
-## Step 8: Run Migration
-
-```bash
-# Test the migration first (dry run)
-python scripts/migrate_to_postgres.py --sqlite tablets.db --postgres postgresql://tablet_user:password@localhost:5432/tablet_management_test
-
-# Verify data in test database
-psql -U tablet_user -d tablet_management_test -c "SELECT COUNT(*) FROM tablets;"
-
-# When ready, migrate to production
-python scripts/migrate_to_postgres.py --sqlite tablets.db --postgres postgresql://tablet_user:password@localhost:5432/tablet_management
-```
-
-## Step 9: Switch to PostgreSQL
-
-```bash
-# Update environment variables
-export DB_TYPE=postgres
-export DB_URL=postgresql://tablet_user:password@localhost:5432/tablet_management
-
-# Restart application
-python app.py
-```
-
-## Step 10: Verify and Monitor
-
-```bash
-# Check application logs for errors
-# Monitor database connections
-psql -U tablet_user -d tablet_management -c "SELECT COUNT(*) FROM tablets;"
-
-# Check active connections
-psql -U postgres -c "SELECT * FROM pg_stat_activity WHERE datname = 'tablet_management';"
-```
-
-## Rollback Plan
-
-If something goes wrong:
-
-1. **Immediate rollback:**
-   ```bash
-   # Switch back to SQLite
-export DB_TYPE=sqlite
-export DB_PATH=tablets.db
-   python app.py
-   ```
-
-2. **Data verification:**
-   ```bash
-   # Compare counts
-   sqlite3 tablets.db "SELECT COUNT(*) FROM tablets;"
-   psql -U tablet_user -d tablet_management -c "SELECT COUNT(*) FROM tablets;"
-   ```
-
-3. **Backup PostgreSQL data:**
-   ```bash
-   pg_dump -U tablet_user -d tablet_management > postgres_backup_$(date +%Y%m%d).sql
-   ```
-
-## Docker Compose (Optional)
-
-For easy deployment with Docker:
-
-```yaml
-# docker-compose.yml
-version: '3.8'
-
-services:
-  postgres:
-    image: postgres:16-alpine
-    container_name: tablet_db
-    environment:
-      POSTGRES_DB: tablet_management
-      POSTGRES_USER: tablet_user
-      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-changeme}
-    ports:
-      - "5432:5432"
-    volumes:
-      - postgres_data:/var/lib/postgresql/data
-    healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U tablet_user -d tablet_management"]
-      interval: 5s
-      timeout: 5s
-      retries: 5
-    restart: unless-stopped
-
-  app:
-    build: .
-    container_name: tablet_app
-    environment:
-      DB_TYPE: postgres
-      DB_URL: postgresql://tablet_user:${POSTGRES_PASSWORD:-changeme}@postgres:5432/tablet_management
-    ports:
-      - "5000:5000"
-    depends_on:
-      postgres:
-        condition: service_healthy
-    restart: unless-stopped
-
-volumes:
-  postgres_data:
-```
-
-Start with Docker:
-```bash
-docker-compose up -d
-```
-
-## Benefits of PostgreSQL
-
-### Performance
-- **Concurrency:** Multiple writers simultaneously (no lock contention)
-- **Indexing:** Advanced index types (B-tree, Hash, GiST, GIN, BRIN)
-- **Query Optimization:** Advanced query planner
-- **Connection Pooling:** Built-in support
-
-### Scalability
-- **Vertical:** Handles large datasets efficiently
-- **Horizontal:** Read replicas, partitioning, sharding
-- **Connections:** Supports thousands of concurrent connections
-
-### Reliability
-- **ACID Compliance:** Full transaction support
-- **Point-in-Time Recovery:** Restore to any moment
-- **Replication:** Master-slave, synchronous, asynchronous
-- **Backups:** `pg_dump`, `pg_basebackup`, continuous archiving
-
-### Security
-- **Authentication:** Multiple methods (password, MD5, SCRAM, LDAP, Kerberos)
-- **Authorization:** Role-based access control (RBAC)
-- **Row-Level Security:** Policies for fine-grained access
-- **Encryption:** SSL, at-rest encryption
-
-### Features
-- **JSON Support:** Native JSON/JSONB data type
-- **Full-Text Search:** Advanced text search capabilities
-- **Arrays:** Store arrays of values
-- **Custom Types:** Create your own data types
-- **Triggers:** Automatic actions on events
-- **Stored Procedures:** Server-side functions
-
-## Monitoring PostgreSQL
-
-### Basic Queries
-
-```sql
--- Active connections
-SELECT * FROM pg_stat_activity WHERE datname = 'tablet_management';
-
--- Table sizes
-SELECT table_name, pg_size_pretty(pg_total_relation_size(table_name))
-FROM information_schema.tables WHERE table_schema = 'public';
-
--- Index usage
-SELECT indexrelname, idx_scan, idx_tup_read, idx_tup_fetch
-FROM pg_stat_user_indexes;
-
--- Slow queries (requires pg_stat_statements extension)
-SELECT query, total_time, calls, mean_time
-FROM pg_stat_statements ORDER BY mean_time DESC LIMIT 10;
-```
-
-### Enable pg_stat_statements
-
-```sql
--- In PostgreSQL
-CREATE EXTENSION pg_stat_statements;
-
--- Then in postgresql.conf
-shared_preload_libraries = 'pg_stat_statements'
-pg_stat_statements.track = all
-```
-
-## Maintenance Tasks
-
-### Regular Maintenance
-
-```bash
-# Vacuum (reclaim space, update statistics)
-vacuumdb -U tablet_user -d tablet_management --analyze
-
-# Reindex (rebuild indexes)
-reindexdb -U tablet_user -d tablet_management
-```
-
-### Backup Strategy
-
-```bash
-# Daily backup
-pg_dump -U tablet_user -d tablet_management > /backups/tablet_management_$(date +%Y%m%d).sql
-
-# Compressed backup
-pg_dump -U tablet_user -d tablet_management | gzip > /backups/tablet_management_$(date +%Y%m%d).sql.gz
-
-# Continuous archiving (WAL)
-# In postgresql.conf:
-wal_level = replica
-archive_mode = on
-archive_command = 'test ! -f /backups/wal/%f && cp %p /backups/wal/%f'
-```
-
-## Performance Optimization
-
-### Configuration Tuning
-
-```conf
-# postgresql.conf recommendations
-shared_buffers = 4GB                   # 25% of total RAM
-work_mem = 16MB                        # For complex sorts
-maintenance_work_mem = 512MB          # For VACUUM, index creation
-effective_cache_size = 12GB           # 75% of total RAM
-random_page_cost = 1.1                # SSD: 1.1, HDD: 4.0
-max_worker_processes = 8              # Number of CPU cores
-max_parallel_workers_per_gather = 4   # Parallel query workers
-max_connections = 200                 # Expected max connections
-```
-
-### Index Optimization
-
-```sql
--- Add indexes for common queries
-CREATE INDEX idx_loans_user_status ON loans(user_id, status);
-CREATE INDEX idx_loans_date_range ON loans(loan_date, return_date);
-
--- Partial index for active loans
-CREATE INDEX idx_loans_active ON loans(tablet_id) WHERE status = 'active';
-
--- Composite index for user loans
-CREATE INDEX idx_loans_user_tablet ON loans(user_id, tablet_id);
-```
-
-## Troubleshooting
-
-### Common Issues
-
-**Connection refused:**
-```bash
-# Check if PostgreSQL is running
-sudo systemctl status postgresql
-
-# Check port
-netstat -tuln | grep 5432
-```
-
-**Authentication failed:**
-```bash
-# Verify user and password
-psql -U tablet_user -d tablet_management -h localhost
-
-# Check pg_hba.conf
-sudo nano /etc/postgresql/16/main/pg_hba.conf
-```
-
-**Database does not exist:**
-```bash
-# Create database
-createdb -U postgres tablet_management
-```
-
-**Permission denied:**
-```sql
--- Grant permissions
-GRANT ALL PRIVILEGES ON DATABASE tablet_management TO tablet_user;
-GRANT ALL ON SCHEMA public TO tablet_user;
-```
-
-### Logs
-
-```bash
-# PostgreSQL logs
-sudo tail -f /var/log/postgresql/postgresql-16-main.log
-
-# Application logs
-journalctl -u tablet_management -f
-```
-
-## Conclusion
-
-Migrating from SQLite to PostgreSQL provides:
-- Better performance at scale
-- True concurrency
-- Enhanced reliability
-- Advanced features
-- Production-ready infrastructure
-
-The repository pattern ensures a smooth transition with minimal code changes, and the migration script automates the data transfer process.

pyproject.toml

@@ -5,33 +5,3 @@ description = "Add your description here"
 readme = "README.md"
 requires-python = ">=3.14"
 dependencies = []
-
-[tool.pytest.ini_options]
-testpaths = ["tests"]
-python_files = "test_*.py"
-python_classes = "Test*"
-python_functions = "test_*"
-verbose = 1
-addopts = "-v"
-
-[tool.coverage.run]
-source = ["."]
-omit = [
-    "*/tests/*",
-    "*/.venv/*",
-    "*/__pycache__/*",
-    "*/.git/*",
-    "*/templates/*",
-]
-
-[tool.coverage.report]
-exclude_lines = [
-    "pragma: no cover",
-    "def __repr__",
-    "raise NotImplementedError",
-    "if __name__ == .__main__.:",
-    "if TYPE_CHECKING:",
-]
-
-[tool.coverage.html]
-directory = "htmlcov"

tests/__init__.py

@@ -1,3 +0,0 @@
-"""
-Unit tests for Tablet Management System
-"""

tests/conftest.py

@@ -1,181 +0,0 @@
-"""
-Pytest configuration and fixtures for Tablet Management System tests
-"""
-
-import pytest
-import sqlite3
-import os
-import sys
-from datetime import datetime
-
-# Add project root to path for imports
-sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-
-
-@pytest.fixture
-def test_db_path():
-    """Path to test database"""
-    return 'test_tablets.db'
-
-
-@pytest.fixture
-def init_test_db(test_db_path):
-    """Initialize a fresh test database with schema"""
-    # Remove existing test database if it exists
-    if os.path.exists(test_db_path):
-        os.remove(test_db_path)
-    
-    conn = sqlite3.connect(test_db_path)
-    cursor = conn.cursor()
-    
-    # Create tables
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS tablets (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            brand TEXT NOT NULL,
-            model TEXT NOT NULL,
-            serial_number TEXT UNIQUE NOT NULL,
-            status TEXT DEFAULT 'available',
-            notes TEXT
-        )
-    ''')
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS users (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            name TEXT NOT NULL,
-            email TEXT,
-            phone TEXT,
-            identification TEXT UNIQUE
-        )
-    ''')
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS loans (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            tablet_id INTEGER NOT NULL,
-            user_id INTEGER NOT NULL,
-            loan_date TEXT NOT NULL,
-            return_date TEXT,
-            status TEXT DEFAULT 'active',
-            FOREIGN KEY (tablet_id) REFERENCES tablets (id),
-            FOREIGN KEY (user_id) REFERENCES users (id)
-        )
-    ''')
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS non_loanable_devices (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            brand TEXT NOT NULL,
-            model TEXT NOT NULL,
-            serial_number TEXT UNIQUE NOT NULL,
-            device_type TEXT NOT NULL,
-            location TEXT,
-            status TEXT DEFAULT 'available',
-            notes TEXT,
-            purchase_date TEXT,
-            purchase_cost REAL
-        )
-    ''')
-    
-    conn.commit()
-    conn.close()
-    
-    yield test_db_path
-    
-    # Cleanup: remove test database
-    if os.path.exists(test_db_path):
-        os.remove(test_db_path)
-
-
-@pytest.fixture
-def db_conn(init_test_db):
-    """Get a database connection to the test database"""
-    conn = sqlite3.connect(init_test_db)
-    conn.row_factory = sqlite3.Row
-    yield conn
-    conn.close()
-
-
-@pytest.fixture
-def sample_tablets(db_conn):
-    """Insert sample tablets into test database"""
-    cursor = db_conn.cursor()
-    
-    tablets = [
-        ('Samsung', 'Galaxy Tab S7', 'SN001', 'available'),
-        ('Apple', 'iPad Pro', 'SN002', 'available'),
-        ('Lenovo', 'Tab P11', 'SN003', 'available'),
-        ('Microsoft', 'Surface Pro', 'SN004', 'loaned'),
-    ]
-    
-    for brand, model, serial, status in tablets:
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, ?)
-        ''', (brand, model, serial, status))
-    
-    db_conn.commit()
-    return tablets
-
-
-@pytest.fixture
-def sample_users(db_conn):
-    """Insert sample users into test database"""
-    cursor = db_conn.cursor()
-    
-    users = [
-        ('John Doe', 'john@example.com', '1234567890', 'ID001'),
-        ('Jane Smith', 'jane@example.com', '0987654321', 'ID002'),
-        ('Bob Johnson', 'bob@example.com', '5551234567', 'ID003'),
-    ]
-    
-    for name, email, phone, identification in users:
-        cursor.execute('''
-            INSERT INTO users (name, email, phone, identification)
-            VALUES (?, ?, ?, ?)
-        ''', (name, email, phone, identification))
-    
-    db_conn.commit()
-    return users
-
-
-@pytest.fixture
-def sample_loans(db_conn, sample_tablets, sample_users):
-    """Insert sample loans into test database"""
-    cursor = db_conn.cursor()
-    
-    # Get tablet and user IDs
-    cursor.execute("SELECT id FROM tablets WHERE serial_number = 'SN004'")
-    loaned_tablet = cursor.fetchone()
-    
-    cursor.execute("SELECT id FROM users WHERE identification = 'ID001'")
-    user1 = cursor.fetchone()
-    
-    cursor.execute("SELECT id FROM users WHERE identification = 'ID002'")
-    user2 = cursor.fetchone()
-    
-    if loaned_tablet and user1:
-        # Active loan for SN004 to user1
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, status)
-            VALUES (?, ?, ?, 'active')
-        ''', (loaned_tablet['id'], user1['id'], loan_date))
-    
-    if user2:
-        # Returned loan for SN001 to user2
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        return_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, return_date, status)
-            VALUES (?, ?, ?, ?, 'returned')
-        ''', (1, user2['id'], loan_date, return_date))
-    
-    db_conn.commit()
-
-
-@pytest.fixture
-def populated_db(db_conn, sample_tablets, sample_users, sample_loans):
-    """Database with all sample data loaded"""
-    return db_conn

tests/requirements.txt

@@ -1,2 +0,0 @@
-pytest==8.3.2
-pytest-cov==5.0.0

tests/test_core.py

@@ -1,481 +0,0 @@
-"""
-Unit tests for core tablet management functions
-Tests loan logic, validation, and database operations
-"""
-
-import pytest
-import sqlite3
-from datetime import datetime
-import sys
-import os
-
-# Import the functions from minimal_app (they work with any db connection)
-sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-
-
-def get_tablet_count(conn):
-    """Helper to get tablet count"""
-    cursor = conn.cursor()
-    cursor.execute("SELECT COUNT(*) FROM tablets")
-    return cursor.fetchone()[0]
-
-
-def get_user_count(conn):
-    """Helper to get user count"""
-    cursor = conn.cursor()
-    cursor.execute("SELECT COUNT(*) FROM users")
-    return cursor.fetchone()[0]
-
-
-def get_loan_count(conn):
-    """Helper to get loan count"""
-    cursor = conn.cursor()
-    cursor.execute("SELECT COUNT(*) FROM loans")
-    return cursor.fetchone()[0]
-
-
-class TestTabletOperations:
-    """Tests for tablet CRUD operations"""
-    
-    def test_add_tablet_success(self, db_conn):
-        """Test adding a new tablet successfully"""
-        cursor = db_conn.cursor()
-        
-        # Add a tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('TestBrand', 'TestModel', 'TEST001'))
-        db_conn.commit()
-        
-        # Verify it was added
-        cursor.execute("SELECT * FROM tablets WHERE serial_number = 'TEST001'")
-        tablet = cursor.fetchone()
-        
-        assert tablet is not None
-        assert tablet['brand'] == 'TestBrand'
-        assert tablet['model'] == 'TestModel'
-        assert tablet['serial_number'] == 'TEST001'
-        assert tablet['status'] == 'available'
-    
-    def test_add_tablet_duplicate_serial(self, db_conn):
-        """Test that duplicate serial numbers are rejected"""
-        cursor = db_conn.cursor()
-        
-        # Add first tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand1', 'Model1', 'DUP001'))
-        db_conn.commit()
-        
-        # Try to add duplicate
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO tablets (brand, model, serial_number, status)
-                VALUES (?, ?, ?, 'available')
-            ''', ('Brand2', 'Model2', 'DUP001'))
-            db_conn.commit()
-    
-    def test_tablet_status_update(self, db_conn):
-        """Test updating tablet status"""
-        cursor = db_conn.cursor()
-        
-        # Add a tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'STATUS001'))
-        db_conn.commit()
-        
-        # Update status
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE serial_number = 'STATUS001'")
-        db_conn.commit()
-        
-        # Verify update
-        cursor.execute("SELECT status FROM tablets WHERE serial_number = 'STATUS001'")
-        status = cursor.fetchone()['status']
-        
-        assert status == 'loaned'
-
-
-class TestUserOperations:
-    """Tests for user CRUD operations"""
-    
-    def test_add_user_success(self, db_conn):
-        """Test adding a new user successfully"""
-        cursor = db_conn.cursor()
-        
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('Test User', 'TESTID001'))
-        db_conn.commit()
-        
-        cursor.execute("SELECT * FROM users WHERE identification = 'TESTID001'")
-        user = cursor.fetchone()
-        
-        assert user is not None
-        assert user['name'] == 'Test User'
-        assert user['identification'] == 'TESTID001'
-    
-    def test_add_user_duplicate_identification(self, db_conn):
-        """Test that duplicate user identifications are rejected"""
-        cursor = db_conn.cursor()
-        
-        # Add first user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User1', 'DUPID001'))
-        db_conn.commit()
-        
-        # Try to add duplicate
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO users (name, identification)
-                VALUES (?, ?)
-            ''', ('User2', 'DUPID001'))
-            db_conn.commit()
-    
-    def test_user_with_contact_info(self, db_conn):
-        """Test adding user with email and phone"""
-        cursor = db_conn.cursor()
-        
-        cursor.execute('''
-            INSERT INTO users (name, email, phone, identification)
-            VALUES (?, ?, ?, ?)
-        ''', ('Contact User', 'test@email.com', '1234567890', 'CONTACT001'))
-        db_conn.commit()
-        
-        cursor.execute("SELECT * FROM users WHERE identification = 'CONTACT001'")
-        user = cursor.fetchone()
-        
-        assert user['email'] == 'test@email.com'
-        assert user['phone'] == '1234567890'
-
-
-class TestLoanOperations:
-    """Tests for loan operations - the core business logic"""
-    
-    def test_loan_tablet_success(self, populated_db):
-        """Test loaning an available tablet to a user"""
-        cursor = populated_db.cursor()
-        
-        # Get an available tablet and user
-        cursor.execute("SELECT id FROM tablets WHERE status = 'available' LIMIT 1")
-        tablet = cursor.fetchone()
-        cursor.execute("SELECT id FROM users LIMIT 1")
-        user = cursor.fetchone()
-        
-        assert tablet is not None
-        assert user is not None
-        
-        tablet_id = tablet['id']
-        user_id = user['id']
-        
-        # Loan the tablet
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet_id,))
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, status)
-            VALUES (?, ?, ?, 'active')
-        ''', (tablet_id, user_id, loan_date))
-        populated_db.commit()
-        
-        # Verify tablet status changed
-        cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet_id,))
-        status = cursor.fetchone()['status']
-        assert status == 'loaned'
-        
-        # Verify loan was created
-        cursor.execute("SELECT * FROM loans WHERE tablet_id = ? AND user_id = ?", (tablet_id, user_id))
-        loan = cursor.fetchone()
-        assert loan is not None
-        assert loan['status'] == 'active'
-        assert loan['return_date'] is None
-    
-    def test_loan_already_loaned_tablet(self, populated_db):
-        """Test that loaning an already loaned tablet fails gracefully"""
-        cursor = populated_db.cursor()
-        
-        # Get a loaned tablet (SN004 should be loaned from sample data)
-        cursor.execute("SELECT id FROM tablets WHERE status = 'loaned' LIMIT 1")
-        tablet = cursor.fetchone()
-        cursor.execute("SELECT id FROM users LIMIT 1")
-        user = cursor.fetchone()
-        
-        if tablet and user:
-            tablet_id = tablet['id']
-            user_id = user['id']
-            
-            # Try to loan it again (should check status first)
-            cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet_id,))
-            status = cursor.fetchone()['status']
-            
-            # This should be 'loaned', so we shouldn't be able to loan it
-            assert status == 'loaned'
-            
-            # The application logic should prevent this
-            # In the actual app, this would be checked before inserting
-            # Here we verify the status is still loaned
-            cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet_id,))
-            final_status = cursor.fetchone()['status']
-            assert final_status == 'loaned'
-    
-    def test_return_tablet_success(self, populated_db):
-        """Test returning a loaned tablet"""
-        cursor = populated_db.cursor()
-        
-        # Get an active loan
-        cursor.execute("SELECT * FROM loans WHERE status = 'active' LIMIT 1")
-        loan = cursor.fetchone()
-        
-        if loan:
-            loan_id = loan['id']
-            tablet_id = loan['tablet_id']
-            
-            # Return the tablet
-            return_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-            cursor.execute('''
-                UPDATE loans SET status = 'returned', return_date = ? WHERE id = ?
-            ''', (return_date, loan_id))
-            cursor.execute("UPDATE tablets SET status = 'available' WHERE id = ?", (tablet_id,))
-            populated_db.commit()
-            
-            # Verify loan status changed
-            cursor.execute("SELECT status, return_date FROM loans WHERE id = ?", (loan_id,))
-            updated_loan = cursor.fetchone()
-            assert updated_loan['status'] == 'returned'
-            assert updated_loan['return_date'] is not None
-            
-            # Verify tablet status changed
-            cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet_id,))
-            tablet_status = cursor.fetchone()['status']
-            assert tablet_status == 'available'
-    
-    def test_return_nonexistent_loan(self, db_conn):
-        """Test returning a loan that doesn't exist"""
-        cursor = db_conn.cursor()
-        
-        # Try to return a non-existent loan
-        cursor.execute("SELECT tablet_id FROM loans WHERE id = ? AND status = 'active'", (9999,))
-        loan = cursor.fetchone()
-        
-        # Should be None since loan doesn't exist
-        assert loan is None
-
-
-class TestEdgeCases:
-    """Tests for edge cases and error conditions"""
-    
-    def test_loan_to_nonexistent_user(self, db_conn):
-        """Test loaning to a user that doesn't exist"""
-        cursor = db_conn.cursor()
-        
-        # Add a tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'EDGE001'))
-        db_conn.commit()
-        
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'EDGE001'")
-        tablet = cursor.fetchone()
-        
-        # Try to loan to non-existent user (ID 9999)
-        # Note: SQLite doesn't enforce foreign keys by default unless we enable it
-        # The application should validate this at the application level
-        # For now, we verify that the user doesn't exist
-        cursor.execute("SELECT id FROM users WHERE id = 9999")
-        user = cursor.fetchone()
-        assert user is None  # User doesn't exist
-        
-        # In a real app with FK enforcement, this would raise IntegrityError
-        # For SQLite without FK enforcement, we just verify the user check
-    
-    def test_loan_nonexistent_tablet(self, db_conn):
-        """Test loaning a tablet that doesn't exist"""
-        cursor = db_conn.cursor()
-        
-        # Add a user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('Test User', 'EDGEID001'))
-        db_conn.commit()
-        
-        cursor.execute("SELECT id FROM users WHERE identification = 'EDGEID001'")
-        user = cursor.fetchone()
-        
-        # Try to loan non-existent tablet (ID 9999)
-        # Note: SQLite doesn't enforce foreign keys by default unless we enable it
-        # The application should validate this at the application level
-        # For now, we verify that the tablet doesn't exist
-        cursor.execute("SELECT id FROM tablets WHERE id = 9999")
-        tablet_check = cursor.fetchone()
-        assert tablet_check is None  # Tablet doesn't exist
-        
-        # In a real app with FK enforcement, this would raise IntegrityError
-        # For SQLite without FK enforcement, we just verify the tablet check
-    
-    def test_empty_database_operations(self, db_conn):
-        """Test operations on empty database"""
-        cursor = db_conn.cursor()
-        
-        # Query empty tables
-        cursor.execute("SELECT COUNT(*) FROM tablets")
-        tablet_count = cursor.fetchone()[0]
-        assert tablet_count == 0
-        
-        cursor.execute("SELECT COUNT(*) FROM users")
-        user_count = cursor.fetchone()[0]
-        assert user_count == 0
-        
-        cursor.execute("SELECT COUNT(*) FROM loans")
-        loan_count = cursor.fetchone()[0]
-        assert loan_count == 0
-    
-    def test_multiple_loans_same_user(self, db_conn):
-        """Test that one user can have multiple loans (one-to-many relationship)"""
-        cursor = db_conn.cursor()
-        
-        # Add user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('MultiLoan User', 'MULTI001'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'MULTI001'")
-        user = cursor.fetchone()
-        
-        # Add multiple tablets
-        for i in range(3):
-            cursor.execute('''
-                INSERT INTO tablets (brand, model, serial_number, status)
-                VALUES (?, ?, ?, 'available')
-            ''', (f'Brand{i}', f'Model{i}', f'MULTI{i:03d}'))
-        db_conn.commit()
-        
-        # Loan all tablets to the same user
-        cursor.execute("SELECT id FROM tablets WHERE serial_number LIKE 'MULTI%'")
-        tablets = cursor.fetchall()
-        
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        for tablet in tablets:
-            cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet['id'],))
-            cursor.execute('''
-                INSERT INTO loans (tablet_id, user_id, loan_date, status)
-                VALUES (?, ?, ?, 'active')
-            ''', (tablet['id'], user['id'], loan_date))
-        db_conn.commit()
-        
-        # Verify user has multiple loans
-        cursor.execute("SELECT COUNT(*) FROM loans WHERE user_id = ?", (user['id'],))
-        loan_count = cursor.fetchone()[0]
-        assert loan_count == 3
-    
-    def test_serial_number_uniqueness_across_tables(self, db_conn):
-        """Test that serial numbers are unique within their respective tables"""
-        cursor = db_conn.cursor()
-        
-        # Add tablet with serial number
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'UNIQUE001'))
-        db_conn.commit()
-        
-        # Add non-loanable device with same serial number (should be allowed - different tables)
-        cursor.execute('''
-            INSERT INTO non_loanable_devices 
-            (brand, model, serial_number, device_type, status)
-            VALUES (?, ?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'UNIQUE001', 'projector'))
-        db_conn.commit()
-        
-        # Both should exist (different tables)
-        cursor.execute("SELECT COUNT(*) FROM tablets WHERE serial_number = 'UNIQUE001'")
-        tablet_count = cursor.fetchone()[0]
-        cursor.execute("SELECT COUNT(*) FROM non_loanable_devices WHERE serial_number = 'UNIQUE001'")
-        device_count = cursor.fetchone()[0]
-        
-        assert tablet_count == 1
-        assert device_count == 1
-        
-        # But duplicate within same table should fail
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO tablets (brand, model, serial_number, status)
-                VALUES (?, ?, ?, 'available')
-            ''', ('Brand2', 'Model2', 'UNIQUE001'))
-            db_conn.commit()
-
-
-class TestQueryOperations:
-    """Tests for query and filtering operations"""
-    
-    def test_query_available_tablets(self, populated_db):
-        """Test querying available tablets"""
-        cursor = populated_db.cursor()
-        
-        cursor.execute("SELECT * FROM tablets WHERE status = 'available'")
-        available = cursor.fetchall()
-        
-        # Should have at least the sample available tablets
-        assert len(available) >= 3  # SN001, SN002, SN003 from sample
-    
-    def test_query_loaned_tablets(self, populated_db):
-        """Test querying loaned tablets"""
-        cursor = populated_db.cursor()
-        
-        cursor.execute("SELECT * FROM tablets WHERE status = 'loaned'")
-        loaned = cursor.fetchall()
-        
-        # Should have at least SN004 from sample data
-        assert len(loaned) >= 1
-    
-    def test_query_active_loans(self, populated_db):
-        """Test querying active loans"""
-        cursor = populated_db.cursor()
-        
-        cursor.execute("SELECT * FROM loans WHERE status = 'active'")
-        active = cursor.fetchall()
-        
-        # Should have at least 1 active loan from sample
-        assert len(active) >= 1
-    
-    def test_query_returned_loans(self, populated_db):
-        """Test querying returned loans"""
-        cursor = populated_db.cursor()
-        
-        cursor.execute("SELECT * FROM loans WHERE status = 'returned'")
-        returned = cursor.fetchall()
-        
-        # Should have at least 1 returned loan from sample
-        assert len(returned) >= 1
-    
-    def test_query_loans_by_user(self, populated_db):
-        """Test querying loans by user"""
-        cursor = populated_db.cursor()
-        
-        cursor.execute("SELECT id FROM users LIMIT 1")
-        user = cursor.fetchone()
-        
-        if user:
-            cursor.execute("SELECT * FROM loans WHERE user_id = ?", (user['id'],))
-            loans = cursor.fetchall()
-            
-            # User should have at least 0 loans
-            assert isinstance(loans, list)
-    
-    def test_query_tablets_by_brand(self, populated_db):
-        """Test querying tablets by brand"""
-        cursor = populated_db.cursor()
-        
-        cursor.execute("SELECT * FROM tablets WHERE brand = 'Samsung'")
-        samsung = cursor.fetchall()
-        
-        # Should find Samsung tablet from sample data
-        assert len(samsung) >= 1
-        assert samsung[0]['brand'] == 'Samsung'

tests/test_edge_cases.py

@@ -1,513 +0,0 @@
-"""
-Edge case tests for Tablet Management System
-Tests critical scenarios: already loaned devices, non-existent loans, duplicates, etc.
-"""
-
-import pytest
-import sqlite3
-from datetime import datetime
-import sys
-import os
-
-sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-
-
-class TestLoanEdgeCases:
-    """Critical edge cases for loan operations"""
-    
-    def test_loan_device_already_loaned(self, db_conn):
-        """
-        CRITICAL: Test that a device already loaned cannot be loaned again
-        This prevents the same physical device from being loaned to multiple users
-        """
-        cursor = db_conn.cursor()
-        
-        # Add a tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'ALREADY_LOANED'))
-        db_conn.commit()
-        
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'ALREADY_LOANED'")
-        tablet = cursor.fetchone()
-        
-        # Add a user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User1', 'USER1'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'USER1'")
-        user1 = cursor.fetchone()
-        
-        # Add another user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User2', 'USER2'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'USER2'")
-        user2 = cursor.fetchone()
-        
-        # Loan to first user
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet['id'],))
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, status)
-            VALUES (?, ?, ?, 'active')
-        ''', (tablet['id'], user1['id'], loan_date))
-        db_conn.commit()
-        
-        # Verify tablet is loaned
-        cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet['id'],))
-        status = cursor.fetchone()['status']
-        assert status == 'loaned'
-        
-        # Try to loan to second user - should check status first
-        # In the actual application, this would be prevented by checking status
-        cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet['id'],))
-        current_status = cursor.fetchone()['status']
-        
-        # The application logic should prevent this
-        assert current_status == 'loaned'
-        
-        # If we tried to loan it anyway (without checking), we'd get a constraint error
-        # because the tablet status is already 'loaned'
-        # The proper app logic checks status before allowing loan
-    
-    def test_return_nonexistent_loan_id(self, db_conn):
-        """
-        CRITICAL: Test returning a loan that doesn't exist
-        Should handle gracefully without crashing
-        """
-        cursor = db_conn.cursor()
-        
-        # Try to return a non-existent loan
-        loan_id = 99999
-        cursor.execute("SELECT tablet_id FROM loans WHERE id = ? AND status = 'active'", (loan_id,))
-        loan = cursor.fetchone()
-        
-        # Should return None (no such loan)
-        assert loan is None
-        
-        # The application should handle this by showing an error message
-        # rather than crashing
-    
-    def test_return_already_returned_loan(self, db_conn):
-        """
-        CRITICAL: Test returning a loan that's already been returned
-        Should handle gracefully
-        """
-        cursor = db_conn.cursor()
-        
-        # Add tablet and user
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'ALREADY_RETURNED'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'ALREADY_RETURNED'")
-        tablet = cursor.fetchone()
-        
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User', 'RETURN_USER'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'RETURN_USER'")
-        user = cursor.fetchone()
-        
-        # Create and return a loan
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        return_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet['id'],))
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, return_date, status)
-            VALUES (?, ?, ?, ?, 'returned')
-        ''', (tablet['id'], user['id'], loan_date, return_date))
-        cursor.execute("UPDATE tablets SET status = 'available' WHERE id = ?", (tablet['id'],))
-        db_conn.commit()
-        
-        # Get the loan ID
-        cursor.execute("SELECT id FROM loans WHERE tablet_id = ?", (tablet['id'],))
-        loan = cursor.fetchone()
-        loan_id = loan['id']
-        
-        # Try to return it again
-        cursor.execute("SELECT tablet_id FROM loans WHERE id = ? AND status = 'active'", (loan_id,))
-        active_loan = cursor.fetchone()
-        
-        # Should be None because status is 'returned', not 'active'
-        assert active_loan is None
-    
-    def test_loan_with_invalid_tablet_id(self, db_conn):
-        """
-        CRITICAL: Test loaning with an invalid/non-existent tablet ID
-        Should fail gracefully
-        """
-        cursor = db_conn.cursor()
-        
-        # Add a user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User', 'INVALID_USER'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'INVALID_USER'")
-        user = cursor.fetchone()
-        
-        # Try to loan with invalid tablet ID
-        invalid_tablet_id = 99999
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        
-        # Note: SQLite doesn't enforce foreign keys by default unless we enable it
-        # The application should validate this at the application level
-        # For now, we verify that the tablet doesn't exist
-        cursor.execute("SELECT id FROM tablets WHERE id = ?", (invalid_tablet_id,))
-        tablet_check = cursor.fetchone()
-        assert tablet_check is None  # Tablet doesn't exist
-        
-        # In a real app with FK enforcement, this would raise IntegrityError
-        # For SQLite without FK enforcement, we just verify the tablet check
-    
-    def test_loan_with_invalid_user_id(self, db_conn):
-        """
-        CRITICAL: Test loaning with an invalid/non-existent user ID
-        Should fail gracefully
-        """
-        cursor = db_conn.cursor()
-        
-        # Add a tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'INVALID_LOAN'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'INVALID_LOAN'")
-        tablet = cursor.fetchone()
-        
-        # Try to loan with invalid user ID
-        invalid_user_id = 99999
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        
-        # Note: SQLite doesn't enforce foreign keys by default unless we enable it
-        # The application should validate this at the application level
-        # For now, we verify that the user doesn't exist
-        cursor.execute("SELECT id FROM users WHERE id = ?", (invalid_user_id,))
-        user_check = cursor.fetchone()
-        assert user_check is None  # User doesn't exist
-        
-        # In a real app with FK enforcement, this would raise IntegrityError
-        # For SQLite without FK enforcement, we just verify the user check
-
-
-class TestDuplicatePrevention:
-    """Tests for preventing duplicate entries"""
-    
-    def test_duplicate_tablet_serial_number(self, db_conn):
-        """
-        CRITICAL: Test that duplicate tablet serial numbers are prevented
-        Serial numbers must be unique for tracking
-        """
-        cursor = db_conn.cursor()
-        
-        # Add first tablet
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand1', 'Model1', 'DUP_SERIAL'))
-        db_conn.commit()
-        
-        # Try to add duplicate
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO tablets (brand, model, serial_number, status)
-                VALUES (?, ?, ?, 'available')
-            ''', ('Brand2', 'Model2', 'DUP_SERIAL'))
-            db_conn.commit()
-    
-    def test_duplicate_user_identification(self, db_conn):
-        """
-        CRITICAL: Test that duplicate user identifications are prevented
-        User identifications must be unique
-        """
-        cursor = db_conn.cursor()
-        
-        # Add first user
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User1', 'DUP_ID'))
-        db_conn.commit()
-        
-        # Try to add duplicate
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO users (name, identification)
-                VALUES (?, ?)
-            ''', ('User2', 'DUP_ID'))
-            db_conn.commit()
-    
-    def test_duplicate_non_loanable_device_serial(self, db_conn):
-        """
-        CRITICAL: Test that duplicate non-loanable device serials are prevented
-        """
-        cursor = db_conn.cursor()
-        
-        # Add first device
-        cursor.execute('''
-            INSERT INTO non_loanable_devices 
-            (brand, model, serial_number, device_type, status)
-            VALUES (?, ?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'DUP_DEVICE_SERIAL', 'projector'))
-        db_conn.commit()
-        
-        # Try to add duplicate
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO non_loanable_devices 
-                (brand, model, serial_number, device_type, status)
-                VALUES (?, ?, ?, ?, 'available')
-            ''', ('Brand2', 'Model2', 'DUP_DEVICE_SERIAL', 'monitor'))
-            db_conn.commit()
-
-
-class TestDataIntegrity:
-    """Tests for data integrity constraints"""
-    
-    def test_foreign_key_tablet_deletion(self, db_conn):
-        """
-        Test that deleting a tablet with active loans is handled
-        SQLite defaults to allowing this, but we should be aware
-        """
-        cursor = db_conn.cursor()
-        
-        # Add tablet and user
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'FK_TEST'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'FK_TEST'")
-        tablet = cursor.fetchone()
-        
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User', 'FK_USER'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'FK_USER'")
-        user = cursor.fetchone()
-        
-        # Create active loan
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet['id'],))
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, status)
-            VALUES (?, ?, ?, 'active')
-        ''', (tablet['id'], user['id'], loan_date))
-        db_conn.commit()
-        
-        # SQLite allows this by default (no ON DELETE RESTRICT)
-        # In production, we might want to add CASCADE or RESTRICT
-        # For now, just verify the loan exists
-        cursor.execute("SELECT COUNT(*) FROM loans WHERE tablet_id = ?", (tablet['id'],))
-        loan_count = cursor.fetchone()[0]
-        assert loan_count == 1
-    
-    def test_null_serial_number_prevention(self, db_conn):
-        """
-        Test that NULL serial numbers are prevented
-        Serial numbers are required (NOT NULL constraint)
-        """
-        cursor = db_conn.cursor()
-        
-        # Try to add tablet with NULL serial number
-        with pytest.raises(sqlite3.IntegrityError):
-            cursor.execute('''
-                INSERT INTO tablets (brand, model, serial_number, status)
-                VALUES (?, ?, ?, 'available')
-            ''', ('Brand', 'Model', None))
-            db_conn.commit()
-    
-    def test_null_identification_prevention(self, db_conn):
-        """
-        Test that NULL user identifications are prevented
-        Identifications are required (NOT NULL constraint)
-        """
-        cursor = db_conn.cursor()
-        
-        # Try to add user with NULL identification
-        # Note: identification is NOT marked as NOT NULL in the schema
-        # This test verifies the current behavior
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User', None))
-        db_conn.commit()
-        
-        # This should work because identification is not NOT NULL
-        # But in practice, we should have this constraint
-        cursor.execute("SELECT COUNT(*) FROM users WHERE identification IS NULL")
-        count = cursor.fetchone()[0]
-        # This will be 1, showing that NULL is currently allowed
-        # In production, we should add NOT NULL constraint
-    
-    def test_empty_string_serial_number(self, db_conn):
-        """
-        Test handling of empty string serial numbers
-        Empty strings are different from NULL
-        """
-        cursor = db_conn.cursor()
-        
-        # Add tablet with empty string serial number
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', ''))
-        db_conn.commit()
-        
-        # This should work (empty string is allowed unless we add CHECK constraint)
-        cursor.execute("SELECT COUNT(*) FROM tablets WHERE serial_number = ''")
-        count = cursor.fetchone()[0]
-        assert count == 1
-        
-        # In production, we might want to prevent empty strings
-        # with a CHECK constraint: CHECK(serial_number <> '')
-
-
-class TestConcurrentScenarioSimulations:
-    """Simulate scenarios that could cause issues in concurrent environments"""
-    
-    def test_loan_return_loan_sequence(self, db_conn):
-        """
-        Test the sequence: loan -> return -> loan again
-        This simulates a device being loaned multiple times over its lifetime
-        """
-        cursor = db_conn.cursor()
-        
-        # Add tablet and user
-        cursor.execute('''
-            INSERT INTO tablets (brand, model, serial_number, status)
-            VALUES (?, ?, ?, 'available')
-        ''', ('Brand', 'Model', 'SEQUENCE_TEST'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'SEQUENCE_TEST'")
-        tablet = cursor.fetchone()
-        
-        cursor.execute('''
-            INSERT INTO users (name, identification)
-            VALUES (?, ?)
-        ''', ('User', 'SEQUENCE_USER'))
-        db_conn.commit()
-        cursor.execute("SELECT id FROM users WHERE identification = 'SEQUENCE_USER'")
-        user = cursor.fetchone()
-        
-        # First loan
-        loan_date1 = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet['id'],))
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, status)
-            VALUES (?, ?, ?, 'active')
-        ''', (tablet['id'], user['id'], loan_date1))
-        db_conn.commit()
-        
-        # Return
-        return_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("SELECT id FROM loans WHERE tablet_id = ?", (tablet['id'],))
-        loan1 = cursor.fetchone()
-        cursor.execute('''
-            UPDATE loans SET status = 'returned', return_date = ? WHERE id = ?
-        ''', (return_date, loan1['id']))
-        cursor.execute("UPDATE tablets SET status = 'available' WHERE id = ?", (tablet['id'],))
-        db_conn.commit()
-        
-        # Second loan
-        loan_date2 = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet['id'],))
-        cursor.execute('''
-            INSERT INTO loans (tablet_id, user_id, loan_date, status)
-            VALUES (?, ?, ?, 'active')
-        ''', (tablet['id'], user['id'], loan_date2))
-        db_conn.commit()
-        
-        # Verify we have 2 loans for this tablet
-        cursor.execute("SELECT COUNT(*) FROM loans WHERE tablet_id = ?", (tablet['id'],))
-        loan_count = cursor.fetchone()[0]
-        assert loan_count == 2
-        
-        # Verify 1 active, 1 returned
-        cursor.execute("SELECT COUNT(*) FROM loans WHERE tablet_id = ? AND status = 'active'", (tablet['id'],))
-        active_count = cursor.fetchone()[0]
-        cursor.execute("SELECT COUNT(*) FROM loans WHERE tablet_id = ? AND status = 'returned'", (tablet['id'],))
-        returned_count = cursor.fetchone()[0]
-        
-        assert active_count == 1
-        assert returned_count == 1
-    
-    def test_multiple_users_multiple_tablets(self, db_conn):
-        """
-        Test complex scenario with multiple users and tablets
-        Ensures the many-to-many relationship works correctly
-        """
-        cursor = db_conn.cursor()
-        
-        # Add 3 users
-        users = []
-        for i in range(3):
-            cursor.execute('''
-                INSERT INTO users (name, identification)
-                VALUES (?, ?)
-            ''', (f'User{i}', f'MULTI_USER_{i}'))
-            db_conn.commit()
-            cursor.execute("SELECT id FROM users WHERE identification = ?", (f'MULTI_USER_{i}',))
-            users.append(cursor.fetchone())
-        
-        # Add 5 tablets
-        tablets = []
-        for i in range(5):
-            cursor.execute('''
-                INSERT INTO tablets (brand, model, serial_number, status)
-                VALUES (?, ?, ?, 'available')
-            ''', (f'Brand{i}', f'Model{i}', f'MULTI_TABLET_{i}'))
-            db_conn.commit()
-            cursor.execute("SELECT id FROM tablets WHERE serial_number = ?", (f'MULTI_TABLET_{i}',))
-            tablets.append(cursor.fetchone())
-        
-        # Loan tablets to users in a pattern
-        # User 0: tablets 0, 1
-        # User 1: tablets 2, 3
-        # User 2: tablet 4
-        loan_date = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
-        
-        loans_map = {
-            users[0]['id']: [tablets[0]['id'], tablets[1]['id']],
-            users[1]['id']: [tablets[2]['id'], tablets[3]['id']],
-            users[2]['id']: [tablets[4]['id']],
-        }
-        
-        for user_id, tablet_ids in loans_map.items():
-            for tablet_id in tablet_ids:
-                cursor.execute("UPDATE tablets SET status = 'loaned' WHERE id = ?", (tablet_id,))
-                cursor.execute('''
-                    INSERT INTO loans (tablet_id, user_id, loan_date, status)
-                    VALUES (?, ?, ?, 'active')
-                ''', (tablet_id, user_id, loan_date))
-        db_conn.commit()
-        
-        # Verify counts
-        cursor.execute("SELECT COUNT(*) FROM loans")
-        total_loans = cursor.fetchone()[0]
-        assert total_loans == 5  # 2 + 2 + 1
-        
-        # Verify each user has correct number of loans
-        for user_id, expected_tablet_ids in loans_map.items():
-            cursor.execute("SELECT COUNT(*) FROM loans WHERE user_id = ?", (user_id,))
-            count = cursor.fetchone()[0]
-            assert count == len(expected_tablet_ids)
-        
-        # Verify all loaned tablets have correct status
-        cursor.execute("SELECT COUNT(*) FROM tablets WHERE status = 'loaned'")
-        loaned_count = cursor.fetchone()[0]
-        assert loaned_count == 5

tests/test_minimal_app.py

@@ -1,365 +0,0 @@
-"""
-Unit tests for the actual application functions from minimal_app.py
-Tests the real business logic with proper imports
-"""
-
-import pytest
-import sqlite3
-import sys
-import os
-from datetime import datetime
-
-# Add project root to path
-sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-
-# Import functions from minimal_app
-from minimal_app import (
-    add_tablet, add_user, loan_tablet, return_tablet,
-    show_available_tablets, show_active_loans, show_loan_history,
-    add_non_loanable_device, show_non_loanable_devices, delete_non_loanable_device
-)
-
-
-@pytest.fixture
-def test_db_path():
-    """Path to test database"""
-    return 'test_minimal_app.db'
-
-
-@pytest.fixture
-def init_test_db(test_db_path):
-    """Initialize a fresh test database with schema (same as minimal_app)"""
-    # Remove existing test database if it exists
-    if os.path.exists(test_db_path):
-        os.remove(test_db_path)
-    
-    # Use the same init_db function from minimal_app
-    from minimal_app import init_db
-    # Temporarily rename the database
-    original_db = 'tablets.db'
-    if os.path.exists(original_db):
-        os.rename(original_db, f'{original_db}.backup')
-    
-    try:
-        # Create test database
-        os.environ['TEST_DB'] = test_db_path
-        init_db()
-        yield test_db_path
-    finally:
-        # Cleanup
-        if os.path.exists(test_db_path):
-            os.remove(test_db_path)
-        if os.path.exists(f'{original_db}.backup'):
-            os.rename(f'{original_db}.backup', original_db)
-        if 'TEST_DB' in os.environ:
-            del os.environ['TEST_DB']
-
-
-@pytest.fixture
-def clean_db():
-    """Fixture that ensures we have a clean database for each test"""
-    # This is simpler - just create a temp database for each test
-    import tempfile
-    import shutil
-    
-    # Create temp directory for database
-    temp_dir = tempfile.mkdtemp()
-    db_path = os.path.join(temp_dir, 'test.db')
-    
-    # Initialize database
-    conn = sqlite3.connect(db_path)
-    cursor = conn.cursor()
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS tablets (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            brand TEXT NOT NULL,
-            model TEXT NOT NULL,
-            serial_number TEXT UNIQUE NOT NULL,
-            status TEXT DEFAULT 'available'
-        )
-    ''')
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS users (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            name TEXT NOT NULL,
-            identification TEXT UNIQUE
-        )
-    ''')
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS loans (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            tablet_id INTEGER NOT NULL,
-            user_id INTEGER NOT NULL,
-            loan_date TEXT NOT NULL,
-            return_date TEXT,
-            status TEXT DEFAULT 'active',
-            FOREIGN KEY (tablet_id) REFERENCES tablets (id),
-            FOREIGN KEY (user_id) REFERENCES users (id)
-        )
-    ''')
-    
-    cursor.execute('''
-        CREATE TABLE IF NOT EXISTS non_loanable_devices (
-            id INTEGER PRIMARY KEY AUTOINCREMENT,
-            brand TEXT NOT NULL,
-            model TEXT NOT NULL,
-            serial_number TEXT UNIQUE NOT NULL,
-            device_type TEXT NOT NULL,
-            location TEXT,
-            status TEXT DEFAULT 'available',
-            notes TEXT,
-            purchase_date TEXT,
-            purchase_cost REAL
-        )
-    ''')
-    
-    conn.commit()
-    conn.close()
-    
-    # Temporarily replace the database
-    original_db = 'tablets.db'
-    backup_path = f'{original_db}.test_backup'
-    
-    # Backup original if exists
-    if os.path.exists(original_db):
-        if os.path.exists(backup_path):
-            os.remove(backup_path)
-        os.rename(original_db, backup_path)
-    
-    # Copy temp db to tablets.db location
-    shutil.copy(db_path, original_db)
-    
-    yield original_db
-    
-    # Cleanup
-    if os.path.exists(original_db):
-        os.remove(original_db)
-    if os.path.exists(backup_path):
-        os.rename(backup_path, original_db)
-    shutil.rmtree(temp_dir, ignore_errors=True)
-
-
-class TestMinimalAppFunctions:
-    """Test the actual functions from minimal_app.py"""
-    
-    def test_add_tablet_function(self, clean_db):
-        """Test the add_tablet function"""
-        add_tablet('TestBrand', 'TestModel', 'TEST_SN_001')
-        
-        # Verify it was added
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        cursor.execute("SELECT * FROM tablets WHERE serial_number = 'TEST_SN_001'")
-        tablet = cursor.fetchone()
-        conn.close()
-        
-        assert tablet is not None
-        assert tablet[1] == 'TestBrand'  # brand is index 1
-        assert tablet[2] == 'TestModel'  # model is index 2
-        assert tablet[3] == 'TEST_SN_001'  # serial_number is index 3
-    
-    def test_add_tablet_duplicate(self, clean_db, capsys):
-        """Test that duplicate serial numbers are rejected"""
-        add_tablet('Brand1', 'Model1', 'DUP_SN')
-        add_tablet('Brand2', 'Model2', 'DUP_SN')
-        
-        captured = capsys.readouterr()
-        assert 'already exists' in captured.out
-    
-    def test_add_user_function(self, clean_db):
-        """Test the add_user function"""
-        add_user('Test User', 'TEST_ID_001')
-        
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        cursor.execute("SELECT * FROM users WHERE identification = 'TEST_ID_001'")
-        user = cursor.fetchone()
-        conn.close()
-        
-        assert user is not None
-        assert user[1] == 'Test User'  # name is index 1
-        assert user[2] == 'TEST_ID_001'  # identification is index 2
-    
-    def test_add_user_duplicate(self, clean_db, capsys):
-        """Test that duplicate user identifications are rejected"""
-        add_user('User1', 'DUP_ID')
-        add_user('User2', 'DUP_ID')
-        
-        captured = capsys.readouterr()
-        assert 'already exists' in captured.out
-    
-    def test_loan_tablet_function(self, clean_db):
-        """Test the loan_tablet function"""
-        # Add tablet and user
-        add_tablet('LoanBrand', 'LoanModel', 'LOAN_SN_001')
-        add_user('LoanUser', 'LOAN_ID_001')
-        
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'LOAN_SN_001'")
-        tablet_id = cursor.fetchone()[0]
-        cursor.execute("SELECT id FROM users WHERE identification = 'LOAN_ID_001'")
-        user_id = cursor.fetchone()[0]
-        conn.close()
-        
-        # Loan the tablet
-        loan_tablet(tablet_id, user_id)
-        
-        # Verify loan was created and tablet status changed
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        
-        cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet_id,))
-        status = cursor.fetchone()[0]
-        assert status == 'loaned'
-        
-        cursor.execute("SELECT * FROM loans WHERE tablet_id = ? AND user_id = ?", (tablet_id, user_id))
-        loan = cursor.fetchone()
-        assert loan is not None
-        assert loan[5] == 'active'  # status is index 5
-        
-        conn.close()
-    
-    def test_loan_already_loaned_tablet(self, clean_db, capsys):
-        """Test loaning a tablet that's already loaned"""
-        add_tablet('Brand', 'Model', 'ALREADY_LOANED_SN')
-        add_user('User1', 'USER1_ID')
-        add_user('User2', 'USER2_ID')
-        
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'ALREADY_LOANED_SN'")
-        tablet_id = cursor.fetchone()[0]
-        cursor.execute("SELECT id FROM users WHERE identification = 'USER1_ID'")
-        user1_id = cursor.fetchone()[0]
-        cursor.execute("SELECT id FROM users WHERE identification = 'USER2_ID'")
-        user2_id = cursor.fetchone()[0]
-        conn.close()
-        
-        # Loan to first user
-        loan_tablet(tablet_id, user1_id)
-        
-        # Try to loan to second user - should fail
-        loan_tablet(tablet_id, user2_id)
-        
-        captured = capsys.readouterr()
-        assert 'not available' in captured.out
-    
-    def test_return_tablet_function(self, clean_db):
-        """Test the return_tablet function"""
-        add_tablet('ReturnBrand', 'ReturnModel', 'RETURN_SN_001')
-        add_user('ReturnUser', 'RETURN_ID_001')
-        
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'RETURN_SN_001'")
-        tablet_id = cursor.fetchone()[0]
-        cursor.execute("SELECT id FROM users WHERE identification = 'RETURN_ID_001'")
-        user_id = cursor.fetchone()[0]
-        conn.close()
-        
-        # Loan the tablet
-        loan_tablet(tablet_id, user_id)
-        
-        # Get loan ID
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        cursor.execute("SELECT id FROM loans WHERE tablet_id = ?", (tablet_id,))
-        loan_id = cursor.fetchone()[0]
-        conn.close()
-        
-        # Return the tablet
-        return_tablet(loan_id)
-        
-        # Verify return
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        
-        cursor.execute("SELECT status FROM tablets WHERE id = ?", (tablet_id,))
-        status = cursor.fetchone()[0]
-        assert status == 'available'
-        
-        cursor.execute("SELECT status, return_date FROM loans WHERE id = ?", (loan_id,))
-        loan = cursor.fetchone()
-        assert loan[0] == 'returned'
-        assert loan[1] is not None  # return_date should be set
-        
-        conn.close()
-    
-    def test_return_nonexistent_loan(self, clean_db, capsys):
-        """Test returning a loan that doesn't exist"""
-        return_tablet(99999)
-        
-        captured = capsys.readouterr()
-        assert 'not found' in captured.out or 'Loan' in captured.out
-    
-    def test_show_available_tablets(self, clean_db, capsys):
-        """Test showing available tablets"""
-        add_tablet('Avail1', 'Model1', 'AVAIL_SN_001')
-        add_tablet('Avail2', 'Model2', 'AVAIL_SN_002')
-        
-        show_available_tablets()
-        
-        captured = capsys.readouterr()
-        assert 'Available Tablets' in captured.out
-        assert 'AVAIL_SN_001' in captured.out
-        assert 'AVAIL_SN_002' in captured.out
-    
-    def test_show_active_loans(self, clean_db, capsys):
-        """Test showing active loans"""
-        add_tablet('LoanBrand', 'LoanModel', 'ACTIVE_LOAN_SN')
-        add_user('LoanUser', 'ACTIVE_LOAN_ID')
-        
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        
-        cursor.execute("SELECT id FROM tablets WHERE serial_number = 'ACTIVE_LOAN_SN'")
-        tablet_id = cursor.fetchone()[0]
-        cursor.execute("SELECT id FROM users WHERE identification = 'ACTIVE_LOAN_ID'")
-        user_id = cursor.fetchone()[0]
-        conn.close()
-        
-        loan_tablet(tablet_id, user_id)
-        show_active_loans()
-        
-        captured = capsys.readouterr()
-        assert 'Active Loans' in captured.out
-        assert 'ACTIVE_LOAN_SN' in captured.out
-    
-    def test_non_loanable_device_crud(self, clean_db, capsys):
-        """Test CRUD operations for non-loanable devices"""
-        # Add
-        add_non_loanable_device('Projector', 'P100', 'PROJ_001', 'projector', 'Room A')
-        captured = capsys.readouterr()
-        assert 'Added non-loanable device' in captured.out
-        
-        # Show
-        show_non_loanable_devices()
-        captured = capsys.readouterr()
-        assert 'PROJ_001' in captured.out
-        
-        # Get ID for delete
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        cursor.execute("SELECT id FROM non_loanable_devices WHERE serial_number = 'PROJ_001'")
-        device_id = cursor.fetchone()[0]
-        conn.close()
-        
-        # Delete
-        delete_non_loanable_device(device_id)
-        captured = capsys.readouterr()
-        assert 'deleted' in captured.out
-        
-        # Verify deletion
-        conn = sqlite3.connect(clean_db)
-        cursor = conn.cursor()
-        cursor.execute("SELECT * FROM non_loanable_devices WHERE serial_number = 'PROJ_001'")
-        device = cursor.fetchone()
-        conn.close()
-        assert device is None