Mocha, Chai, and Sinon Example

sinon_example.js

// `npm install -g mocha`
// `npm install chai sinon`
// Run with `mocha sinon_example.js`

var assert = require('chai').assert;
var sinon = require('sinon');
var clock = sinon.useFakeTimers();

// Sample function, this would normally be where you `require` your modules
var slow = function(cb) {
  setTimeout(function() {
    cb(null, 1);
  }, 500);
};

describe('main', function() {
  it('should work with spies and fake time', function() {
    var callback = sinon.spy();

    slow(callback);
    clock.tick(550); // advance time 550 milliseconds

    assert.isTrue(callback.called);
    assert.equal(callback.callCount, 1);
    assert.isTrue(callback.calledWith(null, 1));
  });

  it('should stub', function() {
    var stub = sinon.stub().returns(25);

    assert.equal(stub(), 25);
    assert.isTrue(stub.calledOnce);
  });
});