I didn't like all the AngularJS wannabes. node.js has perfectly fine module system already.
Inj is a KISS, require based dependency injector (DI) for node.js
requirereader.js
require = require('inj')(module, require);
var fs = require('fs');
exports.text = fs.readFileSync(__dirname + './file.txt', 'utf8');
readerTest.js
// first create container for `reader`
var inj = require('inj');
var container = inj.create(require.resolve('./reader'));
// register a mocked 'fs'
container.register('fs', {readFileSync: function() { return 'foo'; });
var a = require('./reader');
assert(a.text, 'foo');