Deep Instruction · Phases 28–31

Testing + Security + Observability + Performance

Turn production quality into observable, testable engineering rather than a checklist.

Choose the cheapest test that proves the behavior at the correct boundary.

Test invariants using realistic inputs and decisive assertions.

Verify routing, validation, auth, status codes, and persistence together.

Identify assets, actors, entry points, and trust boundaries before selecting controls.

Make one request traceable through distributed steps.

Use different telemetry types for different questions.

Use timings/query plans/profiles to locate the bottleneck before changing code.

Combine tests, logs, metrics, traces, security reasoning, and performance evidence.