# Selenium GRID

**What is Selenium Grid?**  
**Selenium Grid** is a tool that enables you to run Selenium tests simultaneously on multiple machines, operating systems, and browsers. It allows you to run tests in parallel across various environments.  
It consists of:

* **Hub**: The central point that receives test requests and directs them to nodes.
    
* **Nodes**: Machines (or containers) where browsers are launched and tests are executed.
    

### Prerequisites

* Java JDK 8+
    
* Maven
    
* Docker (for Grid setup)
    
* Eclipse
    
* Basic understanding of Selenium
    

**Step 1: Set up Selenium Grid using Docker**  
Using Docker CLI

```bash
docker network create grid
docker run -d -p 4444:4444 --net grid --name selenium-hub selenium/hub
docker run -d --net grid --name chrome-node -e HUB_HOST=selenium-hub selenium/node-chrome
docker run -d --net grid --name firefox-node -e HUB_HOST=selenium-hub selenium/node-firefox
```

**Verify Grid UI to see if the Hub and Nodes are working**  
Visit [`http://localhost:4444/grid`](http://localhost:4444/grid) in your browser to check if the Hub and Nodes are running.

**Step 2: Create a Java Selenium Test**  
Set up a Maven project with the following dependency

```xml
<dependencies>
    <dependency>
        <groupId>org.seleniumhq.selenium</groupId>
        <artifactId>selenium-java</artifactId>
        <version>4.34.0</version>
    </dependency>
</dependencies>
```

**Step 3: Write Test Code to Run on the Grid**

```java
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.remote.RemoteWebDriver;
import org.openqa.selenium.remote.DesiredCapabilities;

import java.net.URL;

public class GridTest {
    public static void main(String[] args) throws Exception {
        // URL of the Grid Hub
        URL gridUrl = new URL("http://localhost:4444/wd/hub");

        // Browser capability (can be "chrome" or "firefox")
        DesiredCapabilities capabilities = new DesiredCapabilities();
        capabilities.setBrowserName("chrome");

        // Create RemoteWebDriver
        WebDriver driver = new RemoteWebDriver(gridUrl, capabilities);

        // Run test
        driver.get("https://example.com");
        System.out.println("Title: " + driver.getTitle());

        driver.quit();
    }
}
```

**Step 4: Run Tests in Parallel**  
You can use a test framework like **TestNG** to run multiple tests in parallel.

```xml
<suite name="GridSuite" parallel="tests" thread-count="2">
    <test name="ChromeTest">
        <parameter name="browser" value="chrome"/>
        <classes>
            <class name="tests.GridTest"/>
        </classes>
    </test>
    <test name="FirefoxTest">
        <parameter name="browser" value="firefox"/>
        <classes>
            <class name="tests.GridTest"/>
        </classes>
    </test>
</suite>
```