Skip to content

feat(learn): clean up code sample & update/correct time mocking section #8707

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
JakobJingleheimer wants to merge 2 commits into
base: main
Choose a base branch
from
Open

feat(learn): clean up code sample & update/correct time mocking section #8707

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ed7e7b7
feat(learn): clean up code sample & update/correct time mocking section
JakobJingleheimer Mar 8, 2026
51af870
fixup!: correct typo
JakobJingleheimer Mar 8, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
45 changes: 22 additions & 23 deletions apps/site/pages/en/learn/test-runner/mocking.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -149,30 +149,27 @@ This leverages [`mock`](https://nodejs.org/api/test.html#class-mocktracker) from

```mjs
import assert from 'node:assert/strict';
import { before, describe, it, mock } from 'node:test';
import { describe, it, mock } from 'node:test';

describe('foo', { concurrency: true }, () => {
describe('foo', { concurrency: true }, async () => {
const barMock = mock.fn();
let foo;

before(async () => {
const barNamedExports = await import('./bar.mjs')
// discard the original default export
.then(({ default: _, ...rest }) => rest);

// It's usually not necessary to manually call restore() after each
// nor reset() after all (node does this automatically).
mock.module('./bar.mjs', {
defaultExport: barMock,
// Keep the other exports that you don't want to mock.
namedExports: barNamedExports,
});

// This MUST be a dynamic import because that is the only way to ensure the
// import starts after the mock has been set up.
({ foo } = await import('./foo.mjs'));
const barNamedExports = await import('./bar.mjs')
// discard the original default export
.then(({ default: _, ...rest }) => rest);

// It's usually not necessary to manually call restore() after each
// nor reset() after all (node does this automatically).
mock.module('./bar.mjs', {
defaultExport: barMock,
// Keep the other exports that you don't want to mock.
namedExports: barNamedExports,
});

// This MUST be a dynamic import because that is the only way to ensure the
// import starts after the mock has been set up.
const { foo } = await import('./foo.mjs');

it('should do the thing', () => {
barMock.mock.mockImplementationOnce(function bar_mock() {
/* … */
Expand Down Expand Up @@ -258,17 +255,19 @@ Note the use of time-zone here (`Z` in the time-stamps). Neglecting to include a
import assert from 'node:assert/strict';
import { describe, it, mock } from 'node:test';

import ago from './ago.mjs';
describe('whatever', { concurrency: true }, async () => {
mock.timers.enable({ now: new Date('2000-01-01T00:02:02Z') });

describe('whatever', { concurrency: true }, () => {
it('should choose "minutes" when that\'s the closet unit', () => {
mock.timers.enable({ now: new Date('2000-01-01T00:02:02Z') });
const { default: ago } = await import('./ago.mjs');

it('should choose "minutes" when that\'s the closest unit', () => {
const t = ago('1999-12-01T23:59:59Z');

assert.equal(t, '2 minutes ago');
});
});
```

`ago` **must** be imported dynamically _after_ `mock.timers` is enabled. As with all module dependency mocking, this is necessary so that the `ago` module receives the mock before the `ago` module is executed (if the mocking does not occur before, it will be too late).

This is especially useful when comparing against a static fixture (that is checked into a repository), such as in [snapshot testing](https://nodejs.org/api/test.html#snapshot-testing).
Loading