Mocha Chai unit testing

hello_world.js

// Load the assertion library
var chai = require('chai'),
    should = chai.should();

describe('Hello world example', function() {

  // This should pass
  it('should be a string', function() {
    var hello_world = 'hello world';
    hello_world.should.be.a('string');
  });

  // This should pass
  it('should have length of 11', function() {
    var hello_world = 'hello world';
    hello_world.should.have.length(11);
  });

  // This should fail
  it('should equal "not even close"', function() {
    var hello_world = 'hello world';
    hello_world.should.equal('not even close');
  });

});