# Low Level Design
All Low Level Design notes →1 — Unit Testing
Covers writing isolated, fast, deterministic tests that verify a single unit of behavior without touching external dependencies.
low-level-design testing-design book
2 — Testable Design
Explains how explicit dependency boundaries and small units of behavior make code inherently easier to exercise in isolation.
low-level-design testing-design book
3 — Mocking
Covers using test doubles to isolate the unit under test from collaborators that are slow, external, or nondeterministic.
low-level-design testing-design book
4 — Dependency Injection for Testing
Explains how injecting dependencies rather than constructing them internally lets tests substitute fakes without touching production code.
low-level-design testing-design book
5 — Contract Testing
Covers verifying that a producer and consumer agree on an API or message contract without standing up the full integration.
low-level-design testing-design book