Selenium Grid Questions & Answers

Question 1:

How do I cut down text execution time for my selenium tests? I want to execute my tests on a combination of different machines and browsers.

Answer

Selenium grid is your friendJ. Selenium grid lets you distribute tests across browsers and machines of your choice.

Question 2:

How does Selenium grid works?

Answer

Selenium grid uses combination of Selenium RC servers to execute tests in multiple browsers on different machine. Herein one Selenium RC server works as hub while other RC servers work as slaves, which could be controlled by hub. Whenever there is a request for a specific configuration for test execution then hub looks for a free RC slave server and if available then test execution begins on it. Once test execution is over then RC slave server would be available for next set of test execution.

Question 3:

Can you show me one diagram which describes functionality of Selenium grid?

Answer

In the following diagram Selenium hub is controlling three Selenium RC servers which are running for configurations –

·         IE on Windows

·         FF on Linux

·         FF on windows

Question 4:

Which jar files are needed to works with Selenium GRID?

Answer

You need to download and add following jar files to your Selenium set up to be able to work with Selenium. These jar files are –

·         selenium-grid-remote-control-standalone-.jar

·         selenium-grid-hub-standalone-.jar

·         selenium-grid-tools-standalone-.jar

Question 5:

How do I start Selenium Grid hub from my machine?

Answer

You should have “ant” set up on your system to be able to work with Grid. Once you have downloaded Selenium Grid, navigate to its distribution directory and execute following command -

ant launch-hub

This would start grid hub on port 4444 locally. You can verify this by navigating to following URL -http://localhost:4444/console

Question 6:

How do I start Selenium Grid Slave Server from my system?

Answer

Navigate to download directory of Selenium gird and execute following command –

ant launch-remote-control

This would launch remote control server at port 555. At this point if you navigate to http://localhost:4444/console then you would see this remote control listed under “Available Remote Controls”

Question 7:

How do I start Selenium grid slave on a different port than 5555?

Answer

You can use option “-Dport” followed by port number to start grid slave on a specific port.

ant -Dport=1111 launch-remote-control

ant -Dport=2222 launch-remote-control

Question 8:

How do I start grid RC slaves on a different system than my local host so than hub could control and contact a specific configuration?

Answer

You should specify following configuration while starting RC slave –

ant -Dport= -Dhost= -DhubURL= launch-remote-control

Herein “hostname” is the host where RC slave is running and “hub url” is URL of machine where grid hub is running.

Question 9:

How do I specify an environment while starting grid slave machine?

Answer

You could specify an environment using “-Denvironment” while starting a slave machine.

ant -Denvironment=”Safari on Mac” launch-remote-control

Herein Safari on Mac is the environment which would be used to recognize configuration of RC slave.

Question 10:

How do I use machine specific configuration in my Selenium tests?

Answer

You could specify machine specific configuration while instantiating Selenium as –

Selenium = new DefaultSelenium("localhost", 4444, **'Safari on Mac'**, 'http://yahoo.com');

And then you use this selenium instance to carryout operation on your web application.

Question 11:

But how does my tests know that ‘Safari on Mac’ mean a safari browser? How does mapping between names like ‘Safari on Mac’ and original browser options available in Selenium work?

Answer

Selenium grid uses a file called “grid_configuration.yml” which defines configurations of all browsers. You would have to add this in your project. This file looks like –

Question 12:

How does Selenium grid hub keeps in touch with RC slave machine?

Answer

Selenium grid hub keeps polling all RC slaves at predefined time to make sure they are available for testing. If not then Selenium hub disconnect any unavailable RC slaves and makes it clear that any RC slave is not available for testing. The deciding parameter is called – “remoteControlPollingIntervalInSeconds” and is defined in “grid_configuration.yml” file.

Question 13:

My RC becomes unresponsive at times and my Selenium grid hub keeps waiting for RC slave to respondL. How do I let hub know to give up on RC slave after a certain time?

Answer

You could state Selenium grid hub to wait for RC slave for a predefined time, and if RC slave does not responds with in this time then hub disconnects test execution on that slave. This parameter is called “sessionMaxIdleTimeInSeconds” and this parameter can be defined in “grid_configuration.yml” file.

Question 14:

What if my hub goes down while Selenium RC slaves are up and running?

Answer

There is one heart beat mechanism from RC slave to hub which is reciprocal to mechanism used by hub to slave machines. RC slaves use a parameter called “hubPollerIntervalInSeconds” to keep track of running grid hub. This parameter can be defined while starting the hub as –

ant -DhubPollerIntervalInSeconds= launch-hub

if hub does not respond within this time then RC slaves deregister themselves from hub.

Question 15:

Can Selenium grid be used for performance testing?

Answer

Selenium grid is for functional testing of application across different configuration. Performance testing is usually not carried out on actual devices but on a simulated http request/response mechanism. If you want to use Selenium Grid for performance testing then you would have to invest heavily on s/w and h/w infrastructure.

Question 16:

Are there additional logs available while working with Selenium grid?

Answer

You can find Selenium grid hub logs in “log/hub.log” and Remote Control logs in “log/rc-*.log” folder.

Question 17:

There are various options available while starting a Selenium server, how do I use them with Selenium grid?

Answer

You can use “seleniumArgs” Java property while launching the remote control and specify any of the option which you would with normal Selenium set up. For example you can run Selenium RC slave in single window mode using following command –

ant -DseleniumArgs="-singleWindow -debug" launch-remote-control

Question 18:

I see duplicate entries in my hub console, same RC slave listed more than once :-O

Answer

This is because you are killing RC slave very ferociously. For example you if you just close the console without actually ending the process in more civil manner. To avoid this you should kill all RC slaves in more civil manner. If you encounter this error then you should restart Selenium hub and RC slaves would them register themselves to hub.

Question 19:

How do I specify my corporate proxy while starting Selenium grid hub or slave machines?

Answer

You could use setting for “http.proxyHost” abd “http.proxyPort” while starting hub and remote control machines –

ant -Dhttp.proxyHost= -Dhttp.proxyPort= launch-hub

ant -Dhttp.proxyHost= -Dhttp.proxyPort= launch-remote-control

Question 20:

How do I use Selenium Grid while using Java, .Net or Ruby

Answer

With java you can take advantage of parallel testing capabilities of TestNG to drive your Selenium grid tests

With .Net you can use “Gallio” to execute your tests in parallel

With Ruby you can use “DeepTest” to distribute your tests

Question 21:

How about the test report when I use Selenium grid for test execution?

Answer

This entirely boils down to framework you use to write your tests. For example in case of java, TestNG reports should suffice.