Reference
Terms used in the lessons
Short definitions for the ideas that recur across the library.
- Verification
- Running a check against the real result. In this library, that often means driving the application through the same steps as a user.
- Feature map
- A catalog of what an app does, how to reach each feature, and what behavior to expect.
- Static analysis
- Checks that inspect code without running the full application, such as type checking and linting.
- Invariant
- A condition that must remain true, such as a renderer never importing a server-only module.
- Worktree
- A separate working directory for a Git repository. It lets another task use a different branch without editing the same checkout.
- Inner loop and outer loop
- The inner loop implements and checks a change. The outer loop gathers new reports, decisions, or alerts and turns them into work.
- Session affinity
- Keeping related requests on a consistent account or backend, often to preserve state or cache reuse.
- Prompt cache
- Reuse of previously processed input. Whether a request qualifies and what it costs depend on the provider and configuration.
- Hydration
- The step in which client-side JavaScript connects interactive behavior to server-rendered page content.
- Synthetic journey
- A scripted sequence of user actions used to measure or test a workflow repeatedly.
- Field data
- Observations from real usage, rather than only a controlled test environment.
- Main thread and worker
- The browser main thread handles much of the interface work. A worker can perform computation separately so that it does not directly block that thread.
- Frame budget
- The time available between display updates. At 120 updates per second, the interval is about 8.3 milliseconds.
- Memoization
- Reusing a computed result when its relevant inputs have not changed.
- Tautological test
- A test that repeats the implementation or derives its expected result from the same logic, so both can be wrong together.
- API-equivalent spend
- What usage would cost under a selected API price table. It is a comparison figure, not cash received or a measure of completed work.
- Diataxis
- A way to distinguish tutorials, how-to guides, reference material, and explanations according to the reader's need.