使用Webdriver从嵌套的promise中返回值

Question

In my test code I wish to achieve the following:

it('Updates label text', function(done) {
   page.testLabelText();
   assert.equal(page.testLabelText().pageLabel, page.testLabelText().iFrameLabel);
   done();
});

In my page object, here is testLabelText(); :

page.testLabelText = function () {
    var pageLabel = function () {
        return driver.findElement(By.css('#element')).getText().then(function(text) {
            return text;
        });
    };
    var iFrameLabel = function () {
        return driver.findElement(By.css('#element')).getText().then(function(text) {
            return text;
        });
    };
    return {
        pageLabel: pageLabel(),
        iFrameLabel: iFrameLabel()
    };
};

But this returns 'Undefined' when printed to the console...I'm a newbie at javascript so though I've managed this in regular javascript, everything I've tried has failed with selenium WebdriverJS promises...

Answer 1

Your assert.equal() is comparing two distinct promise objects so that will never be true. To understand why, here's the step by step. What you need to do is to get the values out of both the promises after they are resolved and then compare the values.

page.testLabelText(); by itself just returns an object so calling it by itself with no assignment of the return value or referencing the return value does nothing.

page.testLabelText().pageLabel by itself is a promise.

page.testLabelText().iFrameLabel by itself is a promise.

And, they are different promise objects so your assert.equal() will not be true.

If you wanted to compare the two values from the promises, you'd have to do something like this:

var obj = page.testLabelText();
Promise.all(obj.pageLabel, obj.iFrameLabel).then(function(results) {
    assert.equal(results[0], results[1]);
    done();
});

Answer 2

The solution was to use an assertion library that could resolve promises in the tests, as this would be impossible using regular async asserts. In this case I used Chai as Promised.

Requiring the following:

chai = require('chai'),
chaiAsPromised = require("chai-as-promised"),
should = chai.should();

and including chai.use(chaiAsPromised); in mocha's before hook, I could then write

it('Updates label text', function() {
  var label = FormsPage.testLabelText();
  label.labelHeading.should.eventually.contain(label.userInput);
});

I found a blog post on this here