Node.js Quality Control & Assurance 4

Question 1

What does `jest.fn()` create?

Accepted Answer

A mock function that records calls and can be configured to return values

Answer

`jest.fn()` returns a mock function with a `.mock` property tracking calls, arguments, return values, and instances.

Question 2

Which tool is commonly used to enforce consistent code formatting in Node.js projects?

Accepted Answer

Prettier

Answer

Prettier is an opinionated code formatter that rewrites code to a consistent style, whereas ESLint focuses on code quality rules.

Question 3

In Supertest, what does `request(app).get('/users').expect(200)` verify?

Accepted Answer

That the HTTP response status code is 200

Answer

`.expect(200)` asserts the response's HTTP status code equals 200, failing the test if the server returns a different code.

Question 4

What is the main purpose of Istanbul (nyc) in a Node.js project?

Accepted Answer

To instrument JavaScript code and measure how much of it is covered by tests

Answer

Istanbul instruments source code at the AST level to track which lines, branches, functions, and statements are executed during tests.

Question 5

Which assertion style does Chai's `expect` interface use?

Accepted Answer

Chainable getter-based natural language assertions

Answer

Chai's `expect` style chains getters and methods like `expect(val).to.be.a('string').and.equal('hello')` to form readable assertions.

Node.js Practice Test