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Selenium Grid - Overview
Selenium Grid is used to execute test scripts in parallel mode by spinning the execution across more than one machine. Thus the Selenium Grid helps to kick off test execution of test scripts by directing the commands from the clients to the instances of the remote browser.
Selenium Grid is a tool that distributes the tests across multiple physical or virtual machines so that we can execute scripts in parallel (simultaneously). It dramatically accelerates the testing process, and runs the tests across multiple browsers and platforms and gives us quick and accurate feedback on the product.
Selenium Grid allows us to execute multiple instances of WebDriver or Selenium Remote Control allows execution of tests in parallel which use the same code base, hence the code need not be present on the system they execute. The selenium-server-standalone package includes Hub, WebDriver, and Selenium RC to execute the scripts in grid.
Selenium Grid has a Hub and a Node. Selenium has released several versions of the Selenium Grid, the latest version is on 4. Selenium Grid 4 is a new implementation and does not utilize the source code of the older Selenium Grid versions.
What is a Selenium Grid?
Selenium Grid is mainly used for parallel testing. It follows a hub(which is a central part and rest are considered as nodes) and node architecture. Selenium Grid enables us to execute varied tests in multiple machines simultaneously. Selenium Grid is used mostly with the intent of test execution rather than design.
Selenium Grid acts as a proxy server to help in triggering parallel execution across multiple machines. This is done by providing direction to the remote web browser objects. Among them, one of them works as a hub.
Next, the hub directs the test instructions to the Selenium Grid nodes which are registered. These test instructions are mainly in JSON format. The hub is instrumental in creating concurrent execution on different machines, controlling various browsers from the center.
Selenium Grid allows scattered execution of test cases. While designing a test case, the its execution is carried out in the same machine where it is developed. However, once there are a substantial number of test cases in a test suite, local execution is not done any more to save time. Instead, multiple servers are utilized and the local machine segregates and runs the tests on various servers or machines.
Need of Selenium Grid
Selenium Grid gives the privilege of executing the test scripts across multiple browsers, and their various versions, more than one instance of the same browser, and platforms thereby it mainly reduces the execution time of the test cases. Selenium Grid allows better utilization of resources by triggering execution across more than one machine.
Selenium Grid gives the option to create a cross browser testing similar to a one single test working on various browsers, and platforms at one go, thereby helping in capturing results, and studying them. The test results are obtained at a faster rate thus helping in providing faster feedback to the product under test.
Components of Selenium Grid
The components of Selenium Grid are listed below −
Hub − It is a server that retrieves the requests from the WebDriver client. It basically obeys the test commands from the client and runs the tests remotely in multiple nodes at the same time. Thus the hub can also be understood as a server which acts as the central point where the tests would be triggered. A Selenium Grid has only one Hub and it is launched on a single machine once.
Node − It is device connected remotely consisting of a remote webdriver, and a native operating system. It gets the hub requests in the JSON format and performs as per the request with the help of the webdriver. Nodes are the Selenium instances that are attached to the Hub which execute the tests. There can be one or more nodes in a grid which can be of any OS and can contain any of the Selenium supported browsers.
Advantages of Selenium Grid
The advantage of Selenium Grid are listed below −
Selenium Grid is used popularly for cross browser testing and to execute tests in different browsers, instances, devices, and platforms. Thus the Selenium Grid gives the opportunity to see how the application under test responds to a wide range of browsers, platforms, and device combinations.
Since tests can be triggered with parallel threads the entire test suite is executed completely with a short test cycle.
Since the test cycles are shorter, Selenium Grid gives quicker results to the project stakeholders and to conclude how the application is developed.
Selenium Grid test cases are flexible, easy to maintain, scalable, and give better test coverage within a short time.
Example
Let us take an example of a Selenium Grid set up where there are two nodes. The first node has the latest version of Chrome, and the other node has Firefox(but not the latest version). As the test is running, the Selenium Grid assigns the tests to execute against configured browsers.
The configuration should be such that execution of tests is accelerated even with the test suite having a large number of tests. Selenium Grid a native part of the Selenium for a long time.
It must also be noted that Selenium Grid allows configuration to be set across platforms. This implies that if the hub executes tests on the Safari browser of the Mac, one node can execute tests on the Chrome browser in Windows, and another node can run tests on the Firefox browser in Ubuntu.
This concludes our comprehensive take on the tutorial on Selenium Grid - Overview. We’ve started with describing what is a Selenium Grid, why is a Selenium Grid needed, what are the components of a Selenium Grid, advantages of Selenium Grid, and examples to walk through how to configure Selenium Grid.
This equips you with in-depth knowledge of the Selenium Grid Overview. It is wise to keep practicing what you’ve learned and exploring others relevant to Selenium to deepen your understanding and expand your horizons.