with-local-tmp-dir

Creates a temporary folder inside cwd, cds inside the folder, runs a function, and removes the folder. Especially useful for testing.

This package can be used to write file-based tests with real files. See below for some examples.

Install

1# npm
2$ npm install with-local-tmp-dir
3
4# Yarn
5$ yarn add with-local-tmp-dir

Basic Usage

1import withLocalTmpDir from 'with-local-tmp-dir';
2import fs from 'fs-extra';
3
4await withLocalTmpDir(() => {
5  console.log(process.cwd());
6  //> /Users/max/project/tmp-18815DudQxmdn03Rz
7
8  // Create some files
9  await fs.outputFile('foo.txt', 'foo bar');
10  await fs.outputFile('bar.txt', 'foo bar');
11})
12// Now the folder does not exist anymore
13
14// The folder is removed even if an exception is thrown
15await withLocalTmpDir(() => {
16  throw new Error('File could not be found')
17});

Reset

Instead of a function you can reset the state yourself instead of passing a function, i.e. change to the previous folder and remove the folder:

1import withLocalTmpDir from 'with-local-tmp-dir';
2import fs from 'fs-extra';
3
4// You can still pass options
5const reset = await withLocalTmpDir();
6
7console.log(process.cwd());
8//> /Users/max/project/tmp-18815DudQxmdn03Rz
9
10// Create some files
11await fs.outputFile('foo.txt', 'foo bar');
12await fs.outputFile('bar.txt', 'foo bar');
13
14await reset();
15
16// Now the folder does not exist anymore

Options

You can pass an options object to the function:

• mode: The file mode to create with, it fallbacks to 0700
• prefix: The optional prefix, fallbacks to tmp- if not provided
• postfix: The optional postfix
• template: mkstemp like filename template, no default
• dir: The base directory, falls back to cwd
• tries: How many times should the function try to get a unique filename before giving up, default 3
• keep: Signals that the temporary file or directory should not be deleted on exit, default is false, means delete
• unsafeCleanup: Recursively removes the created temporary directory, even when it's not empty. default is true

1import withLocalTmpDir from 'with-local-tmp-dir';
2import fs from 'fs-extra';
3
4// do not cleanup if there are files
5await withLocalTmpDir(() => {
6  await fs.outputFile('foo.txt', 'foo bar');
7}, { unsafeCleanup: false });
8
9// run in a subfolder
10await withLocalTmpDir(() => {
11  console.log(process.cwd())
12  //> /Users/max/project/foo/tmp-18815DudQxmdn03Rz
13}, { dir: 'foo' })
14
15// use a different prefix
16await withLocalTmpDir(() => {
17  console.log(process.cwd())
18  //> /Users/max/project/foo-18815DudQxmdn03Rz
19}, { prefix: 'foo' })

Unit Tests with output-files and endent

The most common use case for this package is probably unit tests with Mocha or Jest. The package itself is framework-agnostic, so you can use any of them. To make life easier when writing multiple files with multi-line text content, there are two handy packages: output-files and endent.

The following is an example for Mocha:

1const withLocalTmpDir = require('with-local-tmp-dir')
2const outputFiles = require('output-files')
3const endent = require('endent')
4
5const funcToTest = require('.')
6
7beforeEach(async function () {
8  this.resetWithLocalTmpDir = await withLocalTmpDir()
9})
10
11afterEach(async function () {
12  await this.resetWithLocalTmpDir()
13})
14
15it('works', async () => {
16  await outputFiles({
17    'foo.txt': endent`
18      Lorem ipsum
19      dolor sit
20    `,
21    'index.js': endent`
22      export default {
23        foo: 1,
24        bar: 2,
25      }
26    `,
27  })
28  funcToTest()
29})

Git-based tests

It is also possible to test libraries that make use of Git. You can instantiate a local Git repository inside the temporary folder and run Git operations on it:

1const withLocalTmpDir = require('with-local-tmp-dir')
2const fs = require('fs-extra')
3const execa = require('execa')
4
5beforeEach(async function () {
6  this.resetWithLocalTmpDir = await withLocalTmpDir()
7})
8
9afterEach(async function () {
10  await this.resetWithLocalTmpDir()
11})
12
13it('works', async () => {
14  await execa.command('git init')
15  await execa.command('git config user.email "foo@bar.de"')
16  await execa.command('git config user.name "foo"')
17
18  await outputFile('foo.txt', 'foo bar')
19
20  await execa.command('git add .')
21  await execa.command('git commit -m "feat: init"')
22  funcToTest()
23})

Be careful though, if the repository is not properly initialized, your user Git config might be overridden!

Contribute

Are you missing something or want to contribute? Feel free to file an issue or a pull request! ⚙️

Support

Hey, I am Sebastian Landwehr, a freelance web developer, and I love developing web apps and open source packages. If you want to support me so that I can keep packages up to date and build more helpful tools, you can donate here:

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Thanks a lot for your support! ❤️

See also

• output-files: Output a tree of files and directories by providing an object. Especially useful for testing with real files.
• expect-mocha-image-snapshot: A wrapper around jest-image-snapshot that makes it compatible to Mocha.
• jest-image-matcher: A Jest matcher for image comparisons based on pixelmatch. Can also be used with Mocha. Useful for visual regression testing.
• unify-mocha-output: Adjusts a Mocha output so that it is consistent across platforms and can be used for snapshot testing. Basically adjusts the checkmark symbol and removes time values.
• mock-argv: Temporarily overrides the command line arguments. This is useful for testing.

License

MIT License © Sebastian Landwehr