What is Selenium? Introduction to Selenium Automation Testing

What is Selenium?

Selenium is a free (open source) automated testing suite for web applications across different browsers and platforms. It is quite similar to HP Quick Test Pro (QTP now UFT) only that Selenium focuses on automating web-based applications. Testing done using Selenium tool is usually referred as Selenium Testing.

Selenium is not just a single tool but a suite of software's, each catering to different testing needs of an organization. It has four components.

• Selenium Integrated Development Environment (IDE)
• Selenium Remote Control (RC)
• WebDriver
• Selenium Grid

At the moment, Selenium RC and WebDriver are merged into a single framework to form Selenium 2. Selenium 1, by the way, refers to Selenium RC. 

Since Selenium is a collection of different tools, it had different developers as well. Below are the key persons who made notable contributions to the Selenium Project

The Same Origin Policy Issue

Same Origin policy prohibits JavaScript code from accessing elements from a domain that is different from where it was launched. Example, the HTML code in www.google.com uses a JavaScript program "randomScript.js". The same origin policy will only allow randomScript.js to access pages within google.com such as google.com/mail, google.com/login, or google.com/signup. However, it cannot access pages from different sites such as yahoo.com/search or guru99.com because they belong to different domains.

This is the reason why prior to Selenium RC, testers needed to install local copies of both Selenium Core (a JavaScript program) and the web server containing the web application being tested so they would belong to the same domain

Birth of Selenium Remote Control (Selenium RC)

Unfortunately; testers using Selenium Core had to install the whole application under test and the web server on their own local computers because of the restrictions imposed by the same origin policy. So another ThoughtWork's engineer, Paul Hammant, decided to create a server that will act as an HTTP proxy to "trick" the browser into believing that Selenium Core and the web application being tested come from the same domain. This system became known as the Selenium Remote Control or Selenium 1.

Birth of Selenium Grid

Selenium Grid was developed by Patrick Lightbody to address the need of minimizing test execution times as much as possible. He initially called the system "Hosted QA." It was capable of capturing browser screenshots during significant stages, and also of sending out Selenium commands to different machines simultaneously.

Birth of Selenium IDE

Shinya Kasatani of Japan created Selenium IDE, a Firefox extension that can automate the browser through a record-and-playback feature. He came up with this idea to further increase the speed in creating test cases. He donated Selenium IDE to the Selenium Project in 2006.

Birth of WebDriver

Simon Stewart created WebDriver circa 2006 when browsers and web applications were becoming more powerful and more restrictive with JavaScript programs like Selenium Core. It was the first cross-platform testing framework that could control the browser from the OS level. 

Birth of Selenium 2

In 2008, the whole Selenium Team decided to merge WebDriver and Selenium RC to form a more powerful tool called Selenium 2, with WebDriver being the core. Currently, Selenium RC is still being developed but only in maintenance mode. Most of the Selenium Project's efforts are now focused on Selenium 2.

So, Why the Name Selenium?

It came from a joke which Jason cracked one time to his team. Another automated testing framework was popular during Selenium's development, and it was by the company called Mercury Interactive (yes, the company who originally made QTP before it was acquired by HP). Since Selenium is a well-known antidote for Mercury poisoning, Jason suggested that name. His teammates took it, and so that is how we got to call this framework up to the present.

Selenium Integrated Development Environment (IDE) is the simplest framework in the Selenium suite and is the easiest one to learn. It is a Firefox plugin that you can install as easily as you can with other plugins. However, because of its simplicity, Selenium IDE should only be used as a prototyping tool. If you want to create more advanced test cases, you will need to use either Selenium RC or WebDriver.

Brief Introduction Selenium Remote Control (Selenium RC)

Selenium RC was the flagship testing framework of the whole Selenium project for a long time. This is the first automated web testing tool that allowed users to use a programming language they prefer. As of version 2.25.0, RC can support the following programming languages:

• Java
• C#
• PHP
• Python
• Perl
• Ruby

Brief Introduction WebDriver

The WebDriver proves itself to be better than both Selenium IDE and Selenium RC in many aspects. It implements a more modern and stable approach in automating the browser's actions. WebDriver, unlike Selenium RC, does not rely on JavaScript for Automation. It controls the browser by directly communicating with it.

The supported languages are the same as those in Selenium RC.

• Java
• C#
• PHP
• Python
• Perl
• Ruby

Selenium Grid

Selenium Grid is a tool used together with Selenium RC to run parallel tests across different machines and different browsers all at the same time. Parallel execution means running multiple tests at once.

Features:

• Enables simultaneous running of tests in multiple browsers and environments.
• Saves time enormously.
• Utilizes the hub-and-nodes concept. The hub acts as a central source of Selenium commands to each node connected to it.

Because of their architectural differences, Selenium IDE, Selenium RC, and WebDriver support different sets of browsers and operating environments.

Quick Test Professional(QTP) is a proprietary automated testing tool previously owned by the company Mercury Interactive before it was acquired by Hewlett-Packard in 2006. The Selenium Tool Suite has many advantages over  QTP as detailed below -

Advantages of Selenium over QTP

Advantages of QTP over Selenium

Though clearly, QTP has more advanced capabilities, Selenium outweighs QTP in three main areas:

• Cost(because Selenium is completely free)
• Flexibility(because of a number of programming languages, browsers, and platforms it can support)
• Parallel testing(something that QTP is capable of but only with use of Quality Center)

• The entire Selenium Tool Suite is comprised of four components:
• Selenium IDE, a Firefox add-on that you can only use in creating relatively simple test cases and test suites.
• Selenium Remote Control, also known as Selenium 1, which is the first Selenium tool that allowed users to use programming languages in creating complex tests.
• WebDriver, the newer breakthrough that allows your test scripts to communicate directly to the browser, thereby controlling it from the OS level.
• Selenium Grid is also a tool that is used with Selenium RC to execute parallel tests across different browsers and operating systems.
• Selenium RC and WebDriver was merged to form Selenium 2.
• Selenium is more advantageous than QTP in terms of costs and flexibility. It also allows you to run tests in parallel, unlike in QTP where you are only allowed to run tests sequentially.