servo/tests/wpt/web-platform-tests/fs/resources/sandboxed-fs-test-helpers.js

// This file defines a directory_test() function that can be used to define
// tests that require a FileSystemDirectoryHandle. The implementation of that
// function in this file will return an empty directory in the sandboxed file
// system.
//
// Another implementation of this function exists in
// file-system-access/local-fs-test-helpers.js, where that version uses the
// local file system instead.

function getFileSystemType() {
  return 'sandboxed';
}

async function cleanupSandboxedFileSystem() {
  const dir = await navigator.storage.getDirectory();
  for await (let entry of dir.values())
    await dir.removeEntry(entry.name, {recursive: entry.kind === 'directory'});
}

function directory_test(func, description) {
  promise_test(async t => {
    // To be extra resilient against bad tests, cleanup before every test.
    await cleanupSandboxedFileSystem();

    const dir = await navigator.storage.getDirectory();
    await func(t, dir);
  }, description);
}