Update: If you are looking for a Selenium Grid Tutorial I have put it here
As an application it has great potential since it is has all the best bits of Selenium but it does multiple browsers in parallel. Suddenly your testing that used to take n units of time to run are taking 1/n to run. As a practitioner you can get things done quicker, as a manager you can get things done for cheaper! Everyone is a winner.
The other thing that makes the grid work well, and this is a thing that makes Selenium Remote Control work brilliantly, is the ability to use any language to control the test. People use Java, Ruby, .Net, Python and many more to create their test scripts and run it with the appropriate client. If you have the appropriate client application like TestNG for Java or DeepTest for Ruby or PNUnit for .Net you can start running tests with one script in parallel. The one limitation toof using these test tools is that you only really have one browser application, like Firefox, being tested at a time. This is because you only have one instance of the Selenium object in your code.
The way that I have got around this is to have many instances of the Selenium object in my code that each control a certain type. This type could be Internet Explorer 7 on Vista or Firefox 2 on XP.
An example of this would be (Note: I use c# to create my tests and then run them with NUnit)
[Setup]
public void setup(){
//Vista IE7 Instance
VistaIE7selenium = new DefaultSelenium("hub", 4444, "IE7 on Vista", "http://testserver");
//XP Firefox2 Instance
XPFirefox2selenium = new DefaultSelenium("hub",4444 , "Firefox2 on XP", "http://testserver");
XPFirefox2selenium.Start();
}
[Test]
public void GridTest(){
VistaIE7selenium.Open("/index.html");
XPFirefox2selenium.Open("/index.html");
}
As you can see it has the ability to create multiple instances of Selenium and then run them. This then leaves the handling of the Selenium Remote Control up to the Grid. As Philippe says, "It allows you to gridify your tests".
The negatives of Selenium Grid is that its still a work in progress. I know, thats hardly a reason to call it a negative. There are also a number of bugs but its growing section of OpenQA.org so give it a chance! I have 7 Selenium Remote Control instances running against my Grid (all virtualised with MS Virtual Server and WMWare) and I haven't had many issues. I have hooked Selenium Grid into our CruiseControl.NET server to test all the different browsers. I still have a lot of work to do with this but I know that it will be worth it in the end!
If you want to automate web testing and you want to do it efficiently use Selenium Grid! It will make your life a lot easier!
