Front End Development Quality Control & Assurance 2

Question 1

Which testing approach verifies that individual UI components render correctly in isolation without requiring a full browser environment?

Accepted Answer

Component unit testing

Answer

Component unit testing (e.g., with Jest + React Testing Library) verifies components in isolation without a real browser.

Question 2

What does the 'coverage threshold' setting in a Jest configuration enforce?

Accepted Answer

Minimum percentage of code that must be covered by tests

Answer

Coverage thresholds in Jest fail the test run if the percentage of covered lines, branches, or functions falls below the defined minimum.

Question 3

A Cypress test selector uses `cy.get('[data-testid="submit-btn"]')` instead of `cy.get('.btn-primary')`. What is the primary benefit?

Accepted Answer

Reduced test brittleness when styles change

Answer

Data-testid attributes are decoupled from styling classes, so style refactors don't break selectors.

Question 4

What is a 'snapshot test' in the context of React component testing?

Accepted Answer

A test that serializes rendered output and compares it to a stored baseline

Answer

Snapshot tests serialize a component's rendered output to a file and fail if the output changes unexpectedly.

Question 5

Which accessibility testing tool can be integrated directly into Jest to catch WCAG violations during unit tests?

Accepted Answer

axe-core via jest-axe

Answer

jest-axe wraps axe-core so you can assert `expect(await axe(container)).toHaveNoViolations()` in unit tests.

Front End Development Practice Test