Getting Started Using Selenium-Webdriver JavaScript Bindings in Linux

Getting Started Using Selenium-Webdriver JavaScript Bindings in Linux

I recently fell down the rabbit-hole of web automation testing. It’s been an interesting journey, so I thought I’d document what I’ve learned so far in a series of posts as a reference for others following the same path. Before we go any further, I should point out that I’m still very much a n00b here. These posts are meant to collate information I’ve gathered from across the web into a single resource and clear up some confusion I’ve come across. After reading, you should know how to get some basic test functionality up and running. However, it is not comprehensive.

First, some definitions:

Selenium: Software that automates browsers. Selenium is actually a suite of tools for browser automation. There’s more information on their website.

Webdriver: Is the official W3C specification for interfacing with web browsers. So you tell Selenium what to do to execute your tests, and it controls the browser via webdriver.

Bindings: Where the rubber meets the road. This is how you tell Selenium what to do. You write code and your instructions are executed by Selenium. There are a different set of bindings for each of the supported languages used to control Selenium-Webdriver: Java, C#, Python, Ruby, Perl, PHP, and JavaScript. So, naturally, you’ll need to download and install the package with the bindings you want to use.

I chose the JavaScript package, which was probably a mistake as most of the information you’ll find on the web relates to using Java and there are some differences in the approach. This is one of the reasons I’m writing this post: to help other lost souls searching for help using Selenium-Webdriver with JavaScript bindings.

Right, that’s enough of that. Let’s move on to actually doing stuff.

Download and Install Node.js

The Selenium-Webdriver JavaScript binding comes as a package for Node.js, a stand-alone JS runtime engine. The code you write in JS to control Selenium-Webdriver is executed by the Node.js runtime engine, not the browser itself. I know this seems obvious, but I have noticed some confusion about this on the net, so I thought it was worth mentioning.

First off, install Node.js. There are many pages with instructions covering installation on various Linux distros, including the official Node.js package installation page. When you’re done, check that Node.js is correctly installed and working using the console. If it is, it will report the version number.

$ node --version
v4.6.0

It’s important to note here that Selenium-Webdriver has limited support for different Node.js versions, so the latest and greatest might not work. Make sure the version you install is listed in the Node Support Policy table on the package doc page.

Install Selenium-Webdriver

Once you’ve got Node.js installed, use the node package manager (NPM) to install the Selenium-Webdriver NPM package.

$ npm install selenium-webdriver

Since Selenium-Webdriver is a node module and not an executable, if you want to check it’s all present and correct, you can browse to your node_modules folder. On my machine, it is one level above the bin folder containing the node executable:

$ cd /usr/local/node_modules
$ ls
selenium-webdriver

Install the Browser(s) and Driver(s)

Before we can make Selenium do anything interesting, we need to install browsers (duh ;) and the browser drivers for each browser we want to automate. The bowser driver is an executable written by the browser authors that allows Selenium to control the behaviour of the browser.

Back in the day, before drivers, Selenium used to control the browser by injecting JS commands directly into the page. This is obviously not ideal as it’s implementation-dependant. With the driver abstraction, Selenium can use a single common ‘driver’ interface to talk to each browser driver, which in turn, commands the browser. But I digress.

What’s important is that the browser and its driver are installed and available in your system PATH.

In my case, just to get something up and running, I decided to start from scratch with Chrome for the time being (for ordinary browsing, I use Firefox).

Chrome installation (Ubuntu):

$ sudo apt-get install libxss1 libappindicator1 libindicator7
$ wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb

$ sudo dpkg -i google-chrome*.deb
$ sudo apt-get install -f

Chromedriver installation (Ubuntu):

$ sudo apt-get install unzip

$ wget -N http://chromedriver.storage.googleapis.com/2.20/chromedriver_linux64.zip
$ unzip chromedriver_linux64.zip
$ chmod +x chromedriver

$ sudo mv -f chromedriver /usr/local/share/chromedriver
$ sudo ln -s /usr/local/share/chromedriver /usr/local/bin/chromedriver
$ sudo ln -s /usr/local/share/chromedriver /usr/bin/chromedriver

Executing Your First Test

Finally, we can actually write some code. Create a new file yourFileName.js and save it anywhere convenient. Fire up your favourite text editor and add the following code:

var webdriver = require('/usr/local/node_modules/selenium-webdriver'),
    By = webdriver.By,
    until = webdriver.until;

var driver = new webdriver.Builder()
    .forBrowser('chrome')
    .build();

This code sets up the webdriver and driver objects and allows you to begin controlling the browser. Note that the first line is telling node.js that you need the selenium-webdriver module. I just put the path to the module on my machine to get it up and running. I don’t like this method as it’s brittle, but it’s good enough for now.

Once we’ve set up the environmet, we can start telling the browser what to do:

driver.get('http://www.google.com/ncr');
driver.findElement(By.name('q')).sendKeys('webdriver');
driver.findElement(By.name('btnG')).click();
driver.wait(until.titleIs('webdriver - Google Search'), 1000);
//driver.quit();

This code snippet is from the Selenium-Webdriver node package doc and instructs the browser to perform a google search for the term “webdriver”. If you uncomment out the last line, it will also kill the browser when it’s finished running.

You can see that controlling the browser is done by calling methods on the driver object. For a list of commands and operations you can perform, see this documentation page on the Selenium site. The JavaScript example is always the last of the code snippet examples listed.

To execute the test script, use node from the command line:

$ cd /path/to/your/testScript
$ node testScript.js

That’s it for this post. As you can tell, we’ve barely scratched the surface and there’s plenty more to cover. Stay tuned for the next post in the series dealing with testing environments and JavaScript promises.

As I said at the start, I’m still learning this myself, so comments, suggestions and corrections are welcome :)