Using Selenium grid for parallelization of automated tests

Selenium Grid is a tool that allows you to run Selenium scripts on multiple machines and different browsers concurrently. This can be useful if you want to run your tests in parallel on different machines or different browser configurations.

Here is a step-by-step guide on how to use Selenium Grid:

1. Install the Selenium Server on a machine that will act as the hub. The hub is the central point where you will send your test requests.
2. Install the necessary browser drivers (e.g., ChromeDriver, GeckoDriver) on the hub machine and any other machines that will act as nodes.
3. Start the Selenium Server on the hub machine using the following command:

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

4. Start the Selenium Server on each node machine using the following command:java -jar selenium-server-standalone.jar -role node -hub http://<hub_machine_ip>:4444/grid/register

5. Create a Selenium script that runs your tests. In your script, specify the hub URL and the desired capabilities (e.g., browser name, version, platform) of the node where you want to run your tests. For example:# Set the hub URL and desired capabilities
hub_url = “http://<hub_machine_ip>:4444/wd/hub”
desired_capabilities = {
“browserName”: “chrome”,
“version”: “81.0”,
“platform”: “LINUX”
}# Create the driver and run the tests
driver = webdriver.Remote(hub_url, desired_capabilities)
driver.get(“http://www.example.com”)
# … run your tests
driver.quit()

6. Run your Selenium script. The hub will receive the request and forward it to the appropriate node, executing the tests using the specified browser.

There are a few limitations to using Selenium Grid:

1. Complex setup: Selenium Grid requires setting up a hub and nodes, which can be complex and time-consuming, especially if you want to run tests on multiple platforms and browsers.
2. Slower test execution speed: Selenium Grid can be slower than other testing tools because the tests have to be sent over the network to the hub, which then forwards them to the appropriate node for execution.
3. Scalability limitations: Selenium Grid is limited in terms of how many tests it can run concurrently. The number of tests that can be run in parallel depends on the number of nodes and the resources (e.g., CPU, memory) available on each node.
4. The limited browser and platform support: Selenium Grid only supports a limited number of browsers and platforms. For example, it does not support mobile browsers or native applications.