design
3 free lessons tagged design across Programming, Business. Each one is a short sequence of focused steps with narration and a five-question quiz at the end — take them in any order, no signup required.
Test Doubles: Isolation and What It Costs
Replacing a real dependency with a stand-in is what makes a unit test fast, deterministic, and able to reach states you cannot otherwise produce. It is also how a suite ends up green while the system is broken. This lesson covers the five kinds of double, when each is right, and the two failure modes that follow every team who reaches for mocks by reflex.
Design, Documentation, and the One Act Nobody Can Delegate
Architecture and engineering divide into design, documentation, coordination and administration, and AI touches them very unevenly. This lesson maps the split, then explains the professional seal: a licensed person certifying their own judgement, which is why the responsibility cannot move to a tool.
Crafting Robust APIs: Essential REST Design Principles
Learn the foundational principles behind RESTful API design. This lesson covers statelessness, client-server architecture, uniform interface, effective use of HTTP methods and status codes, and practical tips for building scalable and maintainable web services.