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

# npm
$ npm install with-local-tmp-dir

# Yarn
$ yarn add with-local-tmp-dir

Basic Usage

const withLocalTmpDir = require('with-local-tmp-dir')
const fs = require('fs-extra')

await withLocalTmpDir(() => {
  console.log(process.cwd())
  //> /Users/max/project/tmp-18815DudQxmdn03Rz

  // Create some files
  await fs.outputFile('foo.txt', 'foo bar')
  await fs.outputFile('bar.txt', 'foo bar')
})
// Now the folder does not exist anymore

// The folder is removed even if an exception is thrown
await withLocalTmpDir(() => throw new Error('File could not be found'))

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:

const withLocalTmpDir = require('with-local-tmp-dir')
const fs = require('fs-extra')

// You can still pass options
const reset = await withLocalTmpDir()

console.log(process.cwd())
//> /Users/max/project/tmp-18815DudQxmdn03Rz

// Create some files
await fs.outputFile('foo.txt', 'foo bar')
await fs.outputFile('bar.txt', 'foo bar')

await reset()

// Now the folder does not exist anymore

Options

You can specify an options object that is passed down to tmp-promise. Check the readme for details. Some default values are adjusted, but they still can be overridden.

const withLocalTmpDir = require('with-local-tmp-dir')
const fs = require('fs-extra')

// do not cleanup if there are files
await withLocalTmpDir(() => {
  await fs.outputFile('foo.txt', 'foo bar')
}, { unsafeCleanup: false })

// run in a subfolder
await withLocalTmpDir(() => {
  console.log(process.cwd())
  //> /Users/max/project/foo/tmp-18815DudQxmdn03Rz
}, { dir: 'foo' })

// use a different prefix
await withLocalTmpDir(() => {
  console.log(process.cwd())
  //> /Users/max/project/foo-18815DudQxmdn03Rz
}, { 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:

const withLocalTmpDir = require('with-local-tmp-dir')
const outputFiles = require('output-files')
const endent = require('endent')

const funcToTest = require('.')

beforeEach(async function () {
  this.resetWithLocalTmpDir = await withLocalTmpDir()
})

afterEach(async function () {
  await this.resetWithLocalTmpDir()
})

it('works', async () => {
  await outputFiles({
    'foo.txt': endent`
      Lorem ipsum
      dolor sit
    `,
    'index.js': endent`
      export default {
        foo: 1,
        bar: 2,
      }
    `,
  })
  funcToTest()
})

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:

const withLocalTmpDir = require('with-local-tmp-dir')
const fs = require('fs-extra')
const execa = require('execa')

beforeEach(async function () {
  this.resetWithLocalTmpDir = await withLocalTmpDir()
})

afterEach(async function () {
  await this.resetWithLocalTmpDir()
})

it('works', async () => {
  await execa.command('git init')
  await execa.command('git config user.email "[email protected]"')
  await execa.command('git config user.name "foo"')

  await outputFile('foo.txt', 'foo bar')

  await execa.command('git add .')
  await execa.command('git commit -m "feat: init"')
  funcToTest()
})

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:

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