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Some useful helpers for tests in AVA.


Install ava-patterns by running:

yarn add ava-patterns


Create a temporary directory and delete it (and its contents) at the end of the test.

Takes the following options (all of which are optional):

  • prefix: The directory in which to create the temporary directory. Defaults to a suitable location based on the host system (e.g. /tmp).

Returns an object with the following members:

  • path: The absolute path to the temporary directory.
  • writeFile(filePath, fileContents): Write a file with path relative to the temporary directory, returning the absolute path to the file. Any leading whitespace in the file contents is stripped. If the file starts with a shebang, it is given executable permissions.
import process from 'node:process'
import test from 'ava'
import {useTemporaryDirectory} from 'ava-patterns'

test('writing files to a temporary directory', async (t) => {
  const directory = await useTemporaryDirectory(t)
  await directory.writeFile('file.txt', `
    Hello World!

test('creating temporary directories in a specified location', async (t) => {
  const directory = await useTemporaryDirectory(t, { prefix: process.cwd() })
  await directory.writeFile('file.txt', `
    Hello World!


Spawn a process and kill it at the end of the test.

The second argument supports the following options:

  • command: The command line command as an array of strings.
  • env: An object of environment variables.
  • cwd: The working directory in which to run the command

Returns an object with the following members:

  • output: A string containing all of the output from stdout and stderr.
  • events: An EventEmitter that emits the following events:
    • stdout: Any output written to standard output
    • stderr: Any output written to standard error
    • output: Any output written to either standard output or error
    • exit: The exit code after the process ends
  • waitForOutput(pattern, timeout = 1000): Enables waiting for a given substring or regular expression to be output, for up to a given timeout.
  • waitUntilExit(): Returns a promise that will resolve with the exit code.
  • childProcess: The underlying instance of ChildProcess
import test from 'ava'
import {runProcess} from 'ava-patterns'
import got from 'got'

test('running a Node server', async (t) => {
  const script = `
    import * as http from 'http'
    const server = http.createServer((request, response) => {
      response.end('Hello World!')
    server.listen(10000, () => {

  const program = runProcess(t, {
    command: ['node', '--input-type', 'module', '--eval', script]

  await program.waitForOutput('Listening')

  t.is(program.output, 'Listening\n')

  const response = await got('http://localhost:10000')
  t.is(response.body, 'Hello World!')


Wait for a given number of milliseconds.

import test from 'ava'
import {wait} from 'ava-patterns'

test('writing files', async (t) => {
  // perform action and wait for results
  await wait(500)
  // check results


Make an HTTP request.

It takes in an object with properties method, url, optional headers, and an optional body and returns an object with properties status, headers, and body.

import {http} from 'ava-patterns'

test('sending HTTP requests', async (t) => {
  const response = await http({
    method: 'POST',
    url: 'https://httpbin.org/post',
    body: 'Hello World!'
  t.like(JSON.parse(response.body), {data: 'Hello World!'})




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