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Friday, January 13, 2012

Selenium 1.0 vs Selenium 2.0 aka WebDriver

Selenium 1.0:
Actually Selenium 1.0 consists 2 components.
   1. Selenium Core i.e. Set of pure JavaScript commands
   2. Selenium RC which includes Selenium Server and Selenium Client Lib
In order to execute the JavaScript commands on the web page i.e. Selenium Core commands, the actual Selenium-core JavaScripts should be loaded on the page in which AUT is loading. Also we should make the browser feel as the commands also loading from the same domain from which AUT also loading.(Same Origin Policy)
So we are making a proxy server service called Selenium Server which internally loads our selenium core scripts to the AUT page using a JavaScript Service browserBot.
When a page is opened by selenium server i.e. by RC Server, it have an iFrame.
   a. The iFrame contains a JavaScript service which have our Selenium-Core Scripts loaded.
   b. Inside this iFrame, another frame will be there which contains actual application under test.
Its because of logic of JavaScript function can interoperate with the JavaScript running on the same page. This is the way, thoughtworks team designed to execute javascript commands in a JavaScript enabled web page. ie. Running Selenium commands in webpage through RC Proxy Server using BrowserBot service to interpret the JavaScript expressions ie. actual definitions of Selenese commands.

Selenium Core  = Selenium Base Classes written by pure JavaScript(.js files)
Selenium RC  = Selenium RC Server + Selenium RC Client Lib
      Selenium RC Server = Proxy server to handle the passing commands to webpage and interpreting the commands
      Selenium RC Client Lib = Language bindings to write the tests in different favorite languages
So if you want to extend the functions, you have to add functions to class browserBot in selenium 1.0.
So here you need run your Selenium Server to make the proxy server to bypass the Same Origin Policy problem.

As this is pure JavaScript execution on the web page, we have drawbacks like HTTP to HTTPS transformation handling, Browser dialogs handling for various browsers, handling iframes/frames, Security popups, some KeyBoard/Mouse events et.
This is reason to find another option called WebDriver ie. We are calling it as Selenium 2.0

Selenium 2.0/WebDriver:
Selenium 2.0 consists,
   1. WebDriver API i.e. Native browser API for each browsers.
   2. Selenium Client Lib
So Selenium commands directly interact with browser API. Browser API will interact with browsers via DOM structure after receiving selenese commands from client lib(which are test programs written by us). Thats why for each kind of browser they provided browser specific and supportive methods.
As we told, we have separate drivers like InternetExplorer driver, Firefox driver etc.

Is Selenium Server required if I use Web Driver?
Here no need to use Selenium Server before running your scripts as its using browser API.
Here if you want to extend the functions, you have to add functions to class selenium in selenium 2.0.

But sometimes we need to use Selenium server like
1. If we need to use Selenium grid
2. If we need to execute on remote machines etc.

If you want clear information on how selenium works, see this video.

Also if you are interested in knowing full detailed architecture of selenium WebDriver, view this link.

1 comment:

  1. Selenium WebDriver fits in the same role as RC did, and has incorporated the original 1.x bindings. It refers to both the language bindings and the implementations of the individual browser controlling code. This is commonly referred to as just "WebDriver" or sometimes as Selenium 2.
    Selenium Training Institute in Chennai