JavaScript & TypeScript / Quiz
Snapshots: Rubber Stamp or Regression Net
toMatchSnapshot, the -u reflex, dates that break every run, and the CI flag that stops snapshots from lying by omission.
- Difficulty
- Easy
- Format
- Quiz
- Points
- 100
- Estimate
- 8 min
// MISSION BRIEF
Your Mission
Snapshot testing is the easiest assertion to write and the easiest to stop reading. A snapshot suite is either a regression net or a pile of rubber stamps, and the difference is workflow, not tooling.
This quiz covers how snapshots are written, updated, and reviewed, plus the determinism traps (dates, ids) that make them flake.
Speed bonus active.
// FIRST CONTACT
Battle teaser
The very first run of expect(render(<Badge/>)).toMatchSnapshot() on a machine with no snapshot file:
- AFails, because there is nothing to compare against
- BWrites the snapshot to __snapshots__/... and passes, snapshots assert against their own recorded past, so run one records
- CCompares against an empty string and fails
- DPrompts interactively for approval before writing
Answers, scoring, hints, and the full battle stay sealed.
// SKILL TAGS
javascriptjestsnapshot-testingunit-testing