mock-fs/lib/index.js

var realFs = require('fs');
var path = require('path');

var rewire = require('rewire');

var Binding = require('./binding');
var FileSystem = require('./filesystem');

var minor = process.versions.node.split('.').slice(0, 2).join('.');
var versions = {
  '0.8': 'fs-0.8.26.js',
  '0.9': 'fs-0.9.12.js',
  '0.10': 'fs-0.10.24.js',
  '0.11': 'fs-0.11.10.js'
};

var fsName = versions[minor];
if (!fsName) {
  throw new Error('Unsupported Node version: ' + process.versions.node);
}


/**
 * Hijack the real fs module immediately so the binding can be swapped at will.
 * This works as expected in cases where mock-fs is required before any other
 * module that wraps fs exports.
 */
var mockFs = rewire(path.join(__dirname, '..', 'node', fsName));
var originalBinding = mockFs.__get__('binding');
var originalStats = mockFs.Stats;
for (var name in mockFs) {
  realFs[name] = mockFs[name];
}

function setBinding(binding, Stats) {
  mockFs.__set__('binding', binding);
  mockFs.Stats = realFs.Stats = Stats;
}


/**
 * Swap out the fs bindings for a mock file system.
 * @param {Object} config Mock file system configuration.
 */
var exports = module.exports = function mock(config) {
  var system = FileSystem.create(config);
  var binding = new Binding(system);
  setBinding(binding, binding.Stats);
};


/**
 * Restore the fs bindings for the real file system.
 */
exports.restore = function() {
  setBinding(originalBinding, originalStats);
};


/**
 * Create a mock fs module based on the given file system configuration.
 * @param {Object} config File system configuration.
 * @return {Object} A fs module with a mock file system.
 */
exports.fs = function(config) {
  var system = FileSystem.create(config);
  var binding = new Binding(system);

  // inject the mock binding
  var mockFs = rewire(path.join(__dirname, '..', 'node', fsName));
  mockFs.__set__('binding', binding);

  // overwrite fs.Stats from original binding
  mockFs.Stats = binding.Stats;

  return mockFs;
};


/**
 * Create a file factory.
 */
exports.file = FileSystem.file;


/**
 * Create a directory factory.
 */
exports.directory = FileSystem.directory;


/**
 * Create a symbolic link factory.
 */
exports.symlink = FileSystem.symlink;