How to use the @parcel/fs.OverlayFS function in @parcel/fs

import assert from 'assert';
import vm from 'vm';
import {NodeFS, MemoryFS, OverlayFS, ncp as _ncp} from '@parcel/fs';
import path from 'path';
import WebSocket from 'ws';
import nullthrows from 'nullthrows';

import {makeDeferredWithPromise} from '@parcel/utils';
import _chalk from 'chalk';
import resolve from 'resolve';
import {NodePackageManager} from '@parcel/package-manager';

const workerFarm = createWorkerFarm();
export const inputFS = new NodeFS();
export let outputFS = new MemoryFS(workerFarm);
export let overlayFS = new OverlayFS(outputFS, inputFS);

beforeEach(() => {
  outputFS = new MemoryFS(workerFarm);
  overlayFS = new OverlayFS(outputFS, inputFS);
});

// Recursively copies a directory from the inputFS to the outputFS
export async function ncp(source: FilePath, destination: FilePath) {
  await _ncp(inputFS, source, outputFS, destination);
}

// Mocha is currently run with exit: true because of this issue preventing us
// from properly ending the workerfarm after the test run:
// https://github.com/nodejs/node/pull/28788
//
// TODO: Remove exit: true in .mocharc.json and instead add the following in this file:

beforeEach(() => {
  outputFS = new MemoryFS(workerFarm);
  overlayFS = new OverlayFS(outputFS, inputFS);
});