How to Speed up Test Execution Using Selenium Grid – Selenium Tutorial #29

We are now close to the end of this comprehensive Selenium tutorials series. Next week, we will conclude this online Selenium Training series with “effort estimation of Selenium Projects” and “Selenium Interview questions and answers” tutorials.

Today, in this tutorial we will introduce you with Selenium Grid –  a distributed test execution environment to speed up the execution of a test pass.

What is need of Selenium Grid?

As you go through entire Selenium WebDriver tutorials you will find out WebDriver will execute your test cases in a single machine.

Selenium GRID

Here are few problems with such a setup:

  1. What if you want to execute your test cases for different Operating Systems?
  2. How to run your test cases in different version of same browser?
  3. How to run your test cases for multiple browsers?
  4. Why a scenario should wait for execution of other test cases even if it does not depend upon any test cases?

All these problems are addressed in Selenium GRID.

As we proceed with the Selenium course, we will get the idea about how we can overcome to these problems. Basically Grid architecture is based on master slave architecture. Master machine distributes test cases to different slave machines.

There are 2 versions of Grid available. Selenium Grid 2.0 is the latest from Selenium. Selenium 1.0 was the earlier version. Most of the Selenium experts prefer using Selenium Grid 2.0 as it is packed with new features. Selenium Grid 2.0 supports both Selenium RC and Selenium WebDriver scripts.

Benefits of Selenium Grid:

  1. Selenium Grid gives the flexibility to distribute your test cases for execution.
  2. Reduces batch processing time.
  3. Can perform multi browser testing.
  4. Can perform multi OS testing.

Basic terminology of Selenium Grid:

Hub: Hub is central point to the entire GRID Architecture which receives all requests. There is only one hub in the selenium grid. Hub distributes the test cases across each node.

Node: There can be multiple nodes in Grid. Tests will run in nodes. Each node communicates with the Hub and performs test assigned to it.

Selenium grid Tutorial 1

Install Selenium GRID

Step 1: Download Selenium Server jar file from Selenium’s official website which is formerly known as Selenium RC Server and save it at any location on the local disk.

URL of selenium HQ:

Step 2: Open command prompt and navigate to folder where the server is located. Run the server by using below command

java -jar selenium-server-standalone-2.41.0.jar -role hub

The hub will use the port 4444 by default. This port can be changed by passing the different port number in command prompt provided the port is open and has not been assigned a task.

Status can be checked by using the web interface: http://localhost:4444/grid/console

Step 3: Go to the other machine where you intend to setup Nodes. Open the command prompt and run the below line.

java -jar selenium-server-standalone-2.41.0.jar -role node -hub
http://localhost:4444/grid/register -port 5556

Run the selenium server in other machines to start nodes.

Selenium grid Tutorial 2

Browser and Nodes:

After starting hub and nodes in each machine when you will navigate to GRID Console

You will find 5 Chrome, 5 Firefox and 1 IE browser under Browser section like below.

Selenium grid Tutorial 3

This indicates that by default you can use 5 Chrome, 5 Firefox and 1 IE browser.

For Instance if you want to use only IE you can start the node by using below command:

java -jar selenium-server-standalone-2.41.0.jar -role webdriver -hub
http://localhost:4444/grid/register -port 5556 -browser browserName=iexplore

Verify the browser Type along with other details in GRID Console by clicking on view config.

Selenium grid Tutorial 4

Similarly for Firefox:

java -jar selenium-server-standalone-2.41.0.jar -role webdriver -hub
http://localhost:4444/grid/register -port 5556 -browser browserName=firefox

Selenium grid Tutorial 5

For Chrome:

java -jar selenium-server-standalone-2.41.0.jar -role webdriver -hub
http://localhost:4444/grid/register -port 5556 -browser browserName=chrome

Selenium grid Tutorial 6

There are few scenarios where you may need browser from each type i.e.: IE, Chrome and Firefox.

For instance you may need to use 1 IE and 1 Firefox and 1 Chrome browser

Selenium grid Tutorial 7

java -jar selenium-server-standalone-2.41.0.jar -role webdriver -hub
http://localhost:4444/grid/register -port 5556 -browser browserName=iexplore
-browser browserName=firefox -browser browserName=chrome


maxInstance is used to limit the number of browser initialization in a node.

For example if you want to work with 2 Firefox and 2 IE then you can start the node using maxInstance.

java -jar selenium-server-standalone-2.41.0.jar -role webdriver -hub
http://localhost:4444/grid/register -port 5556 -browser browserName=firefox,maxInstance=3

Maximum instance can be verified under configuration tab.


Selenium grid Tutorial 8

Similarly other browser instances can be configured using maxInstances.


maxSession is used to configure how many number of browsers can be used parallel in the remote system.

java -jar selenium-server-standalone-2.41.0.jar -role webdriver -hub
http://localhost:4444/grid/register -port 5556 -browser browserName=chrome,maxInstance=3
-browser browserName=firefox,maxInstance=3 –maxSession 3

Similarly you can start multiple nodes and configuration can be verified in the console.


Selenium grid Tutorial 9


Selenium grid Tutorial 10

Sample Grid Code:

Here I have used TestNG to run sample GRID test case.

Prerequisite: Create Hub and nodes as explained earlier and TestNG should be configured in eclipse.

Here I have taken sample test to login to Gmail and enter username and password

public class GridExample {
          public void mailTest() throws MalformedURLException{
                   DesiredCapabilities dr=null;
                   RemoteWebDriver driver=new RemoteWebDriver(new     URL("http://localhost:4444/wd/hub"), dr);
                   driver.findElement(By.xpath("//input[@id='Email']")) .sendKeys("username");
                   driver.findElement(By.xpath("//input[@id='Passwd']")) .sendKeys("password");

As in the example you have to use RemoteWebDriver if you are using GRID and you have to provide capabilities to the browser. You have to set the browser and platform as above.

In this example I have used platform as WINDOWS. You can use any platform as per your requirement.

Version of browser can also be set by using dr.setVersion(“version”)

For Instance you need to run this test serially in multiple browsers you have to configure your testng.xml .Below is the testng.xml suite for above test to run your test serially.

<?xml version="1.0" encoding="UTF-8"?>
<suite name="GRID SAMPLE TEST" thread-count="2">
    <parameter name ="browserType" value="IE"/>
            <class name ="GridExample"/>

    <parameter name ="browserType" value="firefox"/>
            <class name ="GridExample"/>

To run the test parallel, you have to change your testng.xml like below.

<?xml version="1.0" encoding="UTF-8"?>
<suite name="GRID SAMPLE TEST" parllel="tests" thread-count="3">
    <parameter name ="browserType" value="firefox"/>
            <class name ="GridExample"/>
    <parameter name ="browserType" value="IE"/>
            <class name ="GridExample"/>

Here in the testng.xml you have to specify parameter as parllel=“tests” and thread-count=“3” describes the maximum number of threads to be executed in parallel.

Configuration using JSON file:

Grid can also be launched along with its configuration by using json configuration file.

Create a json file for having below configuration. Here I have created a json file named as grid_hub.json

  "host": null,
  "port": 4444,
  "newSessionWaitTimeout": -1,
  "servlets" : [],
  "prioritizer": null,
  "capabilityMatcher":   "org.openqa.grid.internal.utils.DefaultCapabilityMatcher",
  "throwOnCapabilityNotPresent": true,
  "nodePolling": 5000,

  "cleanUpCycle": 5000,
  "timeout": 300000,
  "maxSession": 5

Start the hub using below command

java -jar selenium-server-standalone-2.41.0.jar -role hub –hubConfig grid_hub.json

Similarly create different json file for different nodes as per required configuration.

Here is an example of json configuration file for node named as grid_node.json

          "browserName": "chrome",
          "maxInstances": 2
          "browserName": "firefox",
          "maxInstances": 2
          "browserName": "internet explorer",
          "maxInstances": 1




To start the node

java -jar selenium-server-standalone-2.41.0.jar -role rc –nodeConfig grid_node.json

You can change all the configuration of browser, maxInstances, port, maxSession etc. in the json file.

You can provide browser version, platform in the json config file like below

   “browserName”: “chrome”,”version”:”8”,”platform”:”Windows”


It is advisable to use Selenium Grid when you have to perform multi browser testing and you have large number of test cases.

In this module we covered how to setup Grid hub and nodes along with how to run Grid test cases using testng.xml and json file.

Next Tutorial #30: Automation testing with Selenium and Cucumber tool. Cucumber is a BDD testing tool and Framework. We will learn features of Cucumber tool and its usage in real time scenario including how to integrate Selenium WebDriver with Cucumber.

Please post you queries related to Selenium Grid in comments below.


#1 Chris Luck

Hi. this is good training for selenium.

#2 Rahul

Just from experience – Make sure you take care of below point while implementing Grid

1. While running browser instances on node machine – Thumb rule is 1GB for each browser instance .
Otherwise you will get error like
Unable to connect to host on port 7055 after 45000 ms
As Firefox locks this port. Browser need to be started in 45 second otherwise driver will not be able to initiate new browser.

2.Make sure driver instance always QUIT . If it keeps running on node ,node will go out of memory.

3.Standalone server used for node & hub should be same .Its common mistake while upgrading to new version.

#3 Chandra V Pakala

Interesting Article to Brush Up Knowledge in an hour.

#4 Tejaswi

I have created 3 class in testng 1. first class is for launching browser & in second class I am calling first class like class signin extends Launch
& in third class defining in which order that test should run.
when i created hub & node .on the node it only launching the browser signin test is not there is any changes i have to do in xml file??? please help

#5 kalesha shaik


Can any one lemme know, can we run the multiple nodes at a time in a same machine.

I have started the hub and i have mapped a node successfully but when i try to map another node it is saying there is already another node is running.. how ever i can run the node after closing the existing one.

My query is to execute the script in multiple browsers on a same machine.

Thanks inadvance!!

#6 Nimesh Lakhani

above mentioned concept is working at my side. but i am doing database verification testing along with UI testing using selenium. my question is while running selenium script with GRID, how to handle database testing part as in case of “Test of Login” same user will get logged in with multiple browser instances i.e. 3 entries will be posted for same user. in this case how to handle the verification of same activities performed by same user multiple time.


#7 Dan

Hi. Where do you keep the TestNG XML file? In the project? I have my test scripts, and I have my hub and nodes set up. I just don’t know where to put the code to kick off the parallel testing.



#9 Mani

Is it possible from Selenium Grid to Run single test case on multiple machine

#10 muthu

Superb thanks for this topic and i tried in my machine it works.

#11 Bhoomi

HI ,

when we started implementing selenium grid, in our application when we put bulk of data it is printing one word one word slowly instead of taking complete at once. Can anyone let me know the issue and give any suggestion to solve it.


#12 venkatesh

hai good evening thank you i think this will enhance my testing knowledge on selenium and will make me strong to get job

#13 Akshitha

Hi I have got an error when i was running the statement in Node machine.
Exception in thread “main” java.lang.Unsupported ————— Could not find the main class: org.openqa.grid.selenium.Gridlauncher.program

#14 Pandit

Hello Experts,

I want to setup the Automation environment for which I have two options, 1. Standalone selenium server and other is Selenium Grid to run the test in parallel.
I seeking experties help here to know:

What will be the system requirement for both the environment? (Approx test cases will be 500 plus and max 10 testers going to use it)

Your suggestion will be highly appriciable.

Thanks in Advance

#15 Jason

For a typical grid node, how many instances can you have running at once?

I was running 10 instances at a time per node and I was getting OOM errors.

I am having problems determining how much RAM a particular browser uses

#16 Aniruddh Solanki


Can we use 5 firefox instances on each node of grid through Jenkins?

Is it possible?

#17 Karthikeyan Rajendran

why only one internet explorer browser in grid console by default?

By default firefox and chrome have 5 but IE present only one browser in console, we didn’t mentioned like this by default

#18 James Fan

For this line line in class:
RemoteWebDriver driver=new RemoteWebDriver(new URL(“http://localhost:4444/wd/hub”), dr);

Error is show in Eclipse. I think I added all the jar files in the Build Path. (I used Selenium-java-2.44.0). Please let me know what is wrong with it.



#19 tester

“browserType” error…How can i solve this error?
should i create a local variable or access it from testng.xml file please suggest me with some example.

Thank you

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