queue written using TDD

queue.js

function Queue() {
  this.elements = [];
}

Queue.prototype.getSize = function() {
  return this.elements.length;
}

Queue.prototype.push = function(element) {
  this.elements.push(element);
}

Queue.prototype.pop = function() {
  return this.elements.shift();
}

module.exports = Queue;

test.js

var assert = require('assert')
  , Queue = require('./queue');

describe('Queue', function() {
  beforeEach(function(done) {
    queue = new Queue();
    done();
  });

  it('should initialize empty', function() {
    assert.equal(0, queue.getSize());
  });

  it('should return null if attempting to shift while empty', function() {
    assert.equal(null, queue.pop());
  });

  it('should have size of 1 when X is pushed onto it', function() {
    queue.push(0);
    assert.equal(1, queue.getSize());
  });

  it('should have size of 2 when X and Y are pushed onto it', function() {
    queue.push(0);
    queue.push(1);
    assert.equal(2, queue.getSize());
  });

  it('should pop X when X is pushed', function() {
    queue.push(0);
    assert.equal(0, queue.pop());
  });

  it('should pop Y, then X when X and Y are pushed', function() {
    queue.push(0);
    queue.push(1);
    assert.equal(0, queue.pop());
    assert.equal(1, queue.pop());
  });
});