Promise Manager (Protractor – WebDriverJs)

Hey guys,

I have coded in Java, C# and Ruby since I’ve started work with Automation, so about 8 years ago. It’s my first time coding in Javascript for AngularJs pages and for those who are like me you need to know that if you are working with protractor or webdriverjs they return promises from all of its browser interactions, which could lead to some confusing behaviour.

What is the promise manager ?

Protractor and webdriverjs are asynchronous and every result returns a promise. They use a custom promise library called ControlFlow, which implicitly synchronizes asynchronous actions, making it so you only have to register a promise callback when you want to catch an error or access a return value. The promise module coordinates the flow of the asynchronous tasks.

This Promise Manager ensures that calls to the browser are run in sequence, and you only need to worry about dealing with the Promises when you wish to do something with data from the page.

In practice, this means that you can ignore the returned promises while interacting with the page.

So, instead of:

driver.get('https://azevedorafaela.wordpress.com')
 .then(function() {
   return driver.findElement({class: '.searchtip'});
 })
 .then(function(search) {
   return search.sendKeys('webdriver');
 })
 .then(function() {
   return driver.findElement({class: '.button'});
 })
 .then(function(button) {
   return button.click();
 });

You can have:

 driver.get('https://azevedorafaela.wordpress.com');
 driver.findElement({class: '.searchtip'}).sendKeys('webdriver');
 driver.findElement({class: '.button'}).click();

The trick part is when you want to extract the values from the page to do an assertion for example:

 driver.get("https://azevedorafaela.wordpress.com");
    driver.getTitle().then(function(pageTitle) {
        assert.equal(pageTitle, "Rafaela Azevedo");
 });

You can find more information on the links below. Thank you ! See you next weekend 🙂

Resources: http://blog.scottlogic.com/2015/03/04/webdriverjs-and-promises.html

https://github.com/SeleniumHQ/selenium/wiki/WebDriverJs

http://seleniumhq.github.io/selenium/docs/api/javascript/module/selenium-webdriver/lib/promise.html