Test builders in JavaScript using lodash

gistfile1.js

function createTestPerson(override) {
  var defaultPerson = {
    id: 1,
    firstname: 'Bert',
    lastname: 'Macklin'
  }
  return _.merge(defaultPerson, override);
}

var person1 = createTestPerson(),
    person2 = createTestPerson({id:1});