Chai Custom Matcher

test.js

var chai = require('chai');
var expect = chai.expect;
var _ = require('underscore');

chai.use(function (chai, utils) {
  var Assertion = chai.Assertion;

  Assertion.addMethod('created', function (expected, idKey) {
    var obj = this._obj;

    new Assertion(obj[idKey]).to.be.a('string');

    Object.keys(expected).forEach(function (key) {
      new Assertion(obj).to.have.property(key, expected[key]);
    });
  });
});

describe('Test', function() {
  it('should do stuff', function() {
    var genre = {
      id: _.uniqueId(),
      name: 'Jazz'
    };

    expect(genre).to.be.created({
      name: 'Jazz'
    }, 'id');
  });
});