Node.js Quality Control & Assurance 3

Question 1

What does `sinon.stub()` return when called without a replacement implementation?

Accepted Answer

A stub that returns `undefined` by default

Answer

A Sinon stub without a configured behavior returns `undefined` and records all calls, arguments, and call counts.

Question 2

In the Node.js built-in `node:test` module (introduced in Node 18), how do you mark a test as a TODO?

Accepted Answer

Pass `{ todo: true }` as the options object to `test()`

Answer

The options object accepted by `test(name, options, fn)` supports a `todo` property that marks the test as planned but not yet implemented.

Question 3

What is a key advantage of snapshot testing in Jest?

Accepted Answer

It detects unintended changes to component output by comparing against a stored snapshot

Answer

When a snapshot test runs, Jest serializes the value and compares it to the stored `.snap` file, failing if anything changed unexpectedly.

Question 4

Which npm script convention is universally recognized by CI systems and package managers to run tests?

Accepted Answer

"test": "..." in package.json scripts

Answer

`npm test` (or `npm run test`) executes the `test` script defined in `package.json`, and CI platforms like GitHub Actions run it by default.

Question 5

What does the `--exit` flag do in Mocha?

Accepted Answer

Forces Mocha to quit after all tests finish, even if the event loop is still active

Answer

Without `--exit`, Mocha waits for the event loop to drain; `--exit` calls `process.exit()` after tests complete, useful when open handles prevent exit.

Node.js Practice Test

Node.js Practice Test

Node.js Quality Control & Assurance 3