fs-monkey

What is fs-monkey?

The fs-monkey package is a utility library for Node.js that allows you to patch or virtualize the Node.js file system (fs) module. This can be particularly useful for testing purposes, where you might want to avoid performing I/O operations on the actual file system. It provides functionalities to patch the global fs module, or to create a virtual file system that can be used independently.

What are fs-monkey's main functionalities?

Patching the global fs module

This feature allows you to patch the global fs module with a virtual file system. In the code sample, a virtual file system is created with a single file '/foo.txt' containing the text 'bar'. The global fs module is then patched, so any subsequent fs operations in the process will interact with this virtual file system instead of the real one.

const {patchFs} = require('fs-monkey');
const {Volume} = require('memfs');
const vol = Volume.fromJSON({'/foo.txt': 'bar'});
patchFs(vol);

Creating a union file system

This feature allows you to create a union file system, which combines multiple file systems into a single coherent file system interface. In the code sample, a virtual file system is created and then combined with the real fs module using the union file system. This allows for fallback to the real file system for files not found in the virtual file system.

const {ufs} = require('fs-monkey');
const {Volume} = require('memfs');
const vol = Volume.fromJSON({'/foo.txt': 'bar'});
ufs.use(vol);
ufs.use(require('fs'));

Other packages similar to fs-monkey

memfs

Similar to fs-monkey, memfs provides an in-memory file system that mimics the Node.js fs module. While fs-monkey offers utilities to patch or virtualize the fs module, memfs focuses more on creating an in-memory file system that can be used directly or with fs-monkey for patching the global fs.

unionfs

Unionfs is another package that is closely related to fs-monkey, specifically to its union file system functionality. It allows you to transparently overlay multiple file systems into one cohesive file system. While fs-monkey provides this functionality through its ufs feature, unionfs is dedicated solely to creating and managing union file systems.

README

fs-monkey

Monkey-patches for filesystem related things.

• Rewrite require function to load Node's modules from memory.
• Or rewrite the whole fs filesystem module.

Install

npm install --save fs-monkey

Terms

An fs-like object is an object that implements methods of Node's filesystem API. It is denoted as vol:

let vol = {
    readFile: () => { /* ... */ },
    readFileSync: () => { /* ... */ },
    // etc...
}

Reference

• patchFs - rewrites Node's filesystem module fs with fs-like object vol
• patchRequire - rewrites require function, patches Node's module module to use the give fs-like object vol for module loading

License

Unlicense - public domain.