Cannot use 'should' assertion style with mocha / chai / chai-as-promised

[phuvo]

I tried to use myElement.getText().should.eventually.equal("foo") as in the chai-as-promised manual, but got TypeError: Cannot read property 'eventually' of undefined. This is not a problem with chai-as-promised either, because myElement.getText().should.equal("foo") failed with a similar error. Using expect works as expected, though.

var chai = require('chai');
chai.use(require('chai-as-promised'));
var should = chai.should();

describe('Home', function() {
  it('should say hello', function() {
    browser.get('/');
    $('h1').getText().should.eventually.equal('Hello, world');
  });
});

[pcwinters]

I've encountered the same.

[juliemr]

Mocha support is slightly limited - I'd suggest sticking with expect for now :)

If someone has time to look into how should adds itself as a property to everything and why that doesn't work with webdriver promises, please go ahead!

[gabejohnson]

@juliemr I came across the same issue as well. Looking at the code, should adds itself to Object.prototype

https://github.com/chaijs/chai/blob/master/lib/chai/interface/should.js#L35

webdriver.promise.Promise doesn't appear to inherit from Object. It's acting like it comes from a different global context.

(new webdriver.promise.Promise) instanceof Object === false

This isn't an answer, but hopefully it will give someone direction.

[cyberwombat]

Thanks @gabejohnson that got me on the right track. This works:

var chai = require('chai');
var should = chai.should();
var chaiAsPromised = require('chai-as-promised');
chai.use(chaiAsPromised);

Object.defineProperty(protractor.promise.Promise.prototype, 'should', {
  get: Object.prototype.__lookupGetter__('should'),
  set: Object.prototype.__lookupSetter__('should')
});

describe('home page', function() {
  beforeEach(function() {
    browser.ignoreSynchronization = true;
  });

  it('should get home page title', function() {
    browser.get('http://github.com');
    browser.getTitle().should.eventually.equal("GitHub · Build software better, together.");
  });
});

I think a check in Protractor to see if Object has been extended with should would be nice - then Protractor can add that tidibit to extend Promise.

[jlin412]

It breaks the same way in cucumber framework as well using protractor

[jlin412]

Btw, I try codes from @juliemr and it works.

[domenic]

I'd suggest

Object.defineProperty(
  protractor.promise.Promise.prototype,
  'should',
  Object.getOwnPropertyDescriptor(Object.prototype, 'should')
);

[rolandjitsu]

@domenic 👍 works like a charm and it's a bit cleaner than the first version posted here

[vladei]

@domenic I get the following error when i'm trying to use the code. Can you plz help ? : )

TypeError: Property description must be an object: undefined
Stacktrace:
TypeError: Property description must be an object: undefined
at Function.defineProperty (native)
at Object.
main.spec.js:16:8)
at require (module.js:380:17)

[jodytate]

@vladei I received a similar error until I confirmed the following as the correct order:

var chai = require('chai');
var should = chai.should();
var chaiAsPromised = require('chai-as-promised');
chai.use(chaiAsPromised);

Object.defineProperty(
  protractor.promise.Promise.prototype,
  'should',
  Object.getOwnPropertyDescriptor(Object.prototype, 'should')
);

[scottohara]

Note that as of protractor 4.0.0, the workaround above no longer seems to be required (partly due to #3214).

Protractor no longer exposes a Promise object of it's own, and instead defers (no pun intended) to the ManagedPromise object provided by selenium-webdriver.

(Note: if you need to work directly with Promises in protractor 4.0.0, such as protractor.promise.all(), you now need to use the WebDriver promise directly), e.g.

var promise = require('selenium-webdriver').promise;
promise.all([promise1, promise2, promise3])

It would seem that the WebDriver promise inherits from Object.prototype, so initializing chai / chai-as-promised is enough to bestow a should property onto the Promise object, e.g.

// protractor.conf.js

onPrepare() {
  // Load chai assertions
  const chai = require("chai");

  // Load chai-as-promised support
  chai.use(require("chai-as-promised"));

  // Initialise should API (attaches as a property on Object)
  chai.should();
}

[juliemr]

Sweet, closing as fixed.