Notification System Design

A comprehensive exploration of building scalable notification systems with design patterns, SOLID principles, and clean architecture in Python.

This project demonstrates a flexible, extensible notification system using core software engineering principles.

This repo contains the implementation referenced in my blog post Composition over Inheritance: A Notification System Design and serves as the accompanying code sample.

Table of Contents

• Architecture
• Quick Start
• License

Architecture

NotificationService
    ├── Router (resolve channel + provider)
    ├── PolicyPipeline (chain-of-responsibility)
    └── Dispatcher (execute delivery)

Quick Start

Clone the Repository

git clone <repository-url>
cd notification-system-design

Run All Tests

python -m unittest discover tests -v

Test Summary

Overview

• Total Test Cases: 37
• Test Classes: 6
• All Tests: PASSING

Test Breakdown

• TestNotificationService: 20 tests
• TestDefaultRouter: 5 tests
• TestPolicies: 7 tests
• TestChannels: 3 tests
• TestPolicyPipeline: 4 tests

Project Features

• Multiple Channels - Email, SMS, Push notifications
• Policy System - Composable validation, scheduling, retry policies
• Clean Architecture - Clear separation of concerns
• SOLID Principles - Well-designed, maintainable code
• Type Hints - 100% type annotation coverage
• Comprehensive Tests - 37 unit tests
• Zero Dependencies - Pure Python standard library

License

MIT License - See LICENSE file for details