Front End Development Quality Control & Assurance 3

Question 1

Which Lighthouse metric measures the time until the largest visible content element is fully rendered?

Accepted Answer

Largest Contentful Paint (LCP)

Answer

LCP measures when the largest image or text block in the viewport becomes fully visible, targeting under 2.5 seconds.

Question 2

What does 'regression testing' specifically guard against in front-end development?

Accepted Answer

Previously working functionality breaking due to new changes

Answer

Regression tests re-run existing scenarios after changes to confirm that previously working features still work.

Question 3

A developer uses `React Testing Library`'s `userEvent.type()` instead of `fireEvent.change()`. What is the advantage?

Accepted Answer

It simulates real user interactions including keydown, keypress, and keyup events

Answer

userEvent.type() fires the full sequence of keyboard events a real user would generate, making tests more realistic.

Question 4

What is the role of a 'test pyramid' in front-end QA strategy?

Accepted Answer

Having many unit tests, fewer integration tests, and the fewest E2E tests

Answer

The test pyramid advocates for a large base of fast unit tests, a middle layer of integration tests, and a small top of slow E2E tests.

Question 5

When using Playwright for E2E testing, what does `page.waitForSelector()` accomplish?

Accepted Answer

Pauses execution until a matching element appears in the DOM

Answer

waitForSelector pauses the test until the specified element exists and is visible, preventing race conditions.

Front End Development Practice Test