Front End Development Quality Control & Assurance 5

Question 1

What does the `--ci` flag do when running Jest in a continuous integration environment?

Accepted Answer

Disables snapshot updates and fails if new snapshots are written, ensuring no unreviewed changes pass

Answer

With --ci, Jest will fail rather than write new snapshots, preventing accidental snapshot creation from masking real failures in CI.

Question 2

A QA engineer notices that a button works correctly in Chrome but fails in Safari. Which testing practice would have caught this earlier?

Accepted Answer

Cross-browser testing using tools like BrowserStack or Playwright's multi-browser support

Answer

Cross-browser testing runs the same scenarios across multiple browsers and versions to catch engine-specific rendering or API differences.

Question 3

What is the purpose of a 'test double' in unit testing?

Accepted Answer

A generic term for replacing a real dependency (stub, mock, spy, fake) to isolate the unit under test

Answer

Test doubles (mocks, stubs, fakes, spies) replace real collaborators so tests focus on the unit's behavior without external side effects.

Question 4

In front-end performance QA, what does 'Time to Interactive (TTI)' measure?

Accepted Answer

The time until the page is fully interactive and reliably responds to user input

Answer

TTI marks when the main thread is quiet enough and all critical scripts are loaded so the page can respond consistently to user interactions.

Question 5

Which technique allows a team to test a new feature with a subset of real users before full rollout, reducing QA risk?

Accepted Answer

Feature flags (feature toggles) enabling gradual rollout to a percentage of users

Answer

Feature flags let teams enable a feature for a controlled percentage of real users, limiting exposure while validating behavior in production.

Front End Development Practice Test