beginner · self-paced · 4 weeks · 6–8 hrs/week
Jest Unit Testing Deep Dive
Write fast unit suites around pure functions, hooks, and awkward date logic without snapshot sprawl.
¥38,000 JPY — informational list price
Overview
You refactor untestable code just enough to test it, use fake timers responsibly, and keep snapshots disciplined. The tone stays grounded: unit tests support design, they do not replace thinking.
What is included
- Deterministic fake timers for scheduling code
- Parameterized tests that read like tables
- Mock boundaries that do not entangle everything
- Coverage guidance without chasing 100%
- Hook testing patterns for React codebases
- Snapshot hygiene checklist
- Mutation testing intro with pragmatic scope
Outcomes you can evidence
- Shrink flaky unit tests tied to hidden globals
- Explain what coverage is lying about in your repo
- Pick tests worth running on every push vs nightly
Lead mentor
Frontend mentor focused on test-driven refactors and readable assertions.
Avatars load from ui-avatars.com with a styled fallback if blocked.
FAQ
Examples include React hooks, but patterns apply to other frameworks with adapter notes.
Experience notes
“Fake timers module in Jest Unit Testing Deep Dive fixed tests that only broke on CI — small win, loud celebration on our Slack.”
“Snapshot section felt strict in a good way; still trimming old images from our repo this month.”