overleaf/services/document-updater/test/unit/js/module-loader.js

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

module.exports.loadModule = function(filePath, mocks) {
  mocks = mocks || {};

  // this is necessary to allow relative path modules within loaded file
  // i.e. requiring ./some inside file /a/b.js needs to be resolved to /a/some
  var resolveModule = function(module) {
    if (module.charAt(0) !== '.') return module;
    return path.resolve(path.dirname(filePath), module);
  };

  var exports = {};
  var context = {
    require: function(name) {
      return mocks[name] || require(resolveModule(name));
    },
    console: console,
    exports: exports,
    module: {
      exports: exports
    }
  };
  file = fs.readFileSync(filePath);
  vm.runInNewContext(file, context);
  return context;
};