Hands On "AI Engineering"

Hands On "AI Engineering"

Day 31: Unit Testing Services - Building Bulletproof AI Systems

Sep 26, 2025
∙ Paid

Working Code Demo:

What We're Building Today

Today we're implementing comprehensive unit testing for our AI quiz platform's core services. You'll learn to write tests that catch bugs before they reach production, mock external dependencies like AI APIs, and achieve 80% code coverage - the industry standard that separates amateur code from production-ready systems.

Key Deliverables:

  • Complete unit test suite for quiz services

  • Mocking strategy for AI API calls

  • Test coverage reporting and automation

  • CI-ready test pipeline

Why Unit Testing Matters in AI Systems

Traditional web apps fail when users get wrong data. AI systems fail when they make wrong decisions with real consequences. Unit tests are your safety net, catching edge cases before they become user-facing disasters.

Real-World Context: When ChatGPT processes millions of requests daily, unit tests ensure each service component behaves predictably under various conditions. Your quiz platform needs the same reliability.

Component Architecture

Our testing architecture follows the Test Pyramid principle - lots of fast unit tests at the base, fewer integration tests in the middle, minimal end-to-end tests at the top.

The testing layer sits between your business logic and external dependencies, intercepting calls and providing controlled responses. This isolation lets you test complex scenarios without depending on external services.

User's avatar

Continue reading this post for free, courtesy of AI Engineering.

Or purchase a paid subscription.
© 2026 AIE · Privacy ∙ Terms ∙ Collection notice
Start your SubstackGet the app
Substack is the home for great culture