Testing with Fixtures

Frequently, tests need to setup and then tear down some files and directories.

Doing this manually can be very tedious. For example:

// tedious annoying way:
const mkdirp = require('mkdirp')
const rimraf = require('rimraf')
const fs = require('fs')
const {resolve, basename} = require('path')
const t = require('tap')
const dir = resolve(__dirname, basename(__filename, '.js'))
t.teardown(() => rimraf.sync(dir))
fs.writeFileSync(dir + '/some-file', 'some contents')
fs.symlinkSync(dir + '/link', 'some-file')

// ok, now we can finally run some tests!

With the t.testdir() method, you can do this:

// awesome slick way
const dir = t.testdir({
  'some-file': 'some contents',
  // use t.fixture() to create links and symlinks
  // this will use junctions on Windows as of v14.11.0 if the
  // target is a directory, so Administrator perms aren't needed.
  link: t.fixture('symlink', 'some-file'),
  nested: {
    'README.md': 'nested dirs work, too!'

// run tests!

Keeping the Fixture Around

If you need to inspect the fixture directory after running your test, you can either pass { saveFixture: true } to the test creation, or add --save-fixture to the command-line, or set TAP_SAVE_FIXTURE=1 in the environment.

Otherwise, the test fixture will be deleted when the test creating it is finished.

Fixture Arguments

The t.fixture(type, content) method will create a Fixture object with the specified type and content. The supported types are:

  • link - A hardlink to the file specified in content.
  • symlink - A symbolic link to the path specified in content.
  • dir - A directory, where the content is an object describing the children in that directory.
  • file - A file, where the content is the file contents.

You can also pass in a plain JavaScript object to specify a dir type, or a string or buffer to specify a file type. For example, these two styles produce identical results:

// clunky style:
t.testdir(t.fixture('dir', {
  'filename': t.fixture('file', 'contents')

// sugar style:
  filename: 'contents'

Fixture Directory Filename

The fixture directory is returned by the t.testdir() method. It is also available on the t.testdirName getter.

The name is determined by the filename and path of the main script. If no main script is available (for example, if running tap in a node repl), then it uses the test file name TAP.

Timing Caveat

While the fixture directory is created synchronously, it is removed asynchronously, because that is the only way to get around ENOTEMPTY errors on Windows.

This means that the next test after one that uses t.testdir() will be deferred until after the end of the current run to completion. So, for example:

t.test('first test', t => {
t.test('second test', t => {

This will print one two four three instead of one two three four, because the second test is deferred while waiting for the first test's fixture dir to be removed.

The fixture directory cleanup will always happen after any user-scheduled t.teardown() functions, as of tap v14.11.0.