Dependency injection in Node.js

generic-component-tests.js

var chai = require('chai'),
	expect = chai.expect,
	should = chai.should();

describe('unit-tests', function () {
	'use strict'

	describe('generic-component-tests', function () {
		describe('given a component', function () {
			describe('when initialized w/ dependency', function () {
				it('then it should use the dependency injected', function (done) {
					var dependency = { doSomething: function (name) { return 'hello ' + name; } };
					var component = require('../../src/generic-component')(dependency);

					var message = component.getMessage('mattia');

					expect(message).to.be.equal('hello mattia');

					done();
				});
			});

			describe('when initialized w/out dependency', function () {
				it('then it should use the dependency declared internally', function (done) {
					var component = require('../../src/generic-component')();

					var message = component.getMessage('mattia');

					expect(message).to.be.equal('ciao mattia');

					done();
				});
			});
		});
	});
});	

generic-component.js

function genericComponent(dependency) {
	'use strict';

	dependency = dependency || { doSomething: function (name) { return 'ciao ' + name } };

	function getMessage(name) {
		return dependency.doSomething(name);
	}

	return {
		getMessage: getMessage,
	}
}

module.exports = genericComponent;