Module 04 — Automated Testing & Verification

Untested code is legacy code the moment it is written—especially when AI generates it. This module teaches you how to design fast, deterministic unit tests and decouple external dependencies (databases, clocks, HTTP APIs) using Fakes and Dependency Inversion.

Lessons in this Module

1. 01 — Deterministic Unit Testing, AAA & Fixtures Structure tests with Arrange-Act-Assert, test boundary conditions, and eliminate flaky time/randomness dependencies.
2. 02 — Dependency Inversion, Fakes vs Mocks & Boundary Testing Learn why over-mocking creates brittle tests that pass while production breaks, and build lightweight in-memory Fakes instead.