Running Tests on Selenium Grid

Grid is running. Dashboard shows Chrome, Firefox, Edge nodes — all green. Now what? You need to tell your tests to use the Grid instead of local browsers. That means RemoteWebDriver + browser options.

WebDriver Factory — The Smart Way

Don't hardcode the driver creation in every test. Build a factory. One class that knows how to create any browser — locally or on Grid. Every test asks the factory for a driver. The factory figures out where to run it.

utils/WebDriverFactory.javajava

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.firefox.FirefoxOptions;
import org.openqa.selenium.edge.EdgeDriver;
import org.openqa.selenium.edge.EdgeOptions;
import org.openqa.selenium.remote.RemoteWebDriver;
import java.net.URL;

public class WebDriverFactory {

    private static final String GRID_URL =
        System.getProperty("grid.url", "");

    public static WebDriver createDriver(String browser) throws Exception {
        boolean useGrid = !GRID_URL.isEmpty();
        boolean headless = Boolean.parseBoolean(
            System.getProperty("headless", "false"));

        switch (browser.toLowerCase()) {
            case "chrome":
                ChromeOptions chromeOpts = new ChromeOptions();
                if (headless) {
                    chromeOpts.addArguments("--headless=new");
                }
                chromeOpts.addArguments("--no-sandbox");
                chromeOpts.addArguments("--disable-dev-shm-usage");
                chromeOpts.addArguments("--window-size=1920,1080");
                return useGrid
                    ? new RemoteWebDriver(new URL(GRID_URL), chromeOpts)
                    : new ChromeDriver(chromeOpts);

            case "firefox":
                FirefoxOptions ffOpts = new FirefoxOptions();
                if (headless) {
                    ffOpts.addArguments("--headless");
                }
                ffOpts.addArguments("--width=1920");
                ffOpts.addArguments("--height=1080");
                return useGrid
                    ? new RemoteWebDriver(new URL(GRID_URL), ffOpts)
                    : new FirefoxDriver(ffOpts);

            case "edge":
                EdgeOptions edgeOpts = new EdgeOptions();
                if (headless) {
                    edgeOpts.addArguments("--headless=new");
                }
                edgeOpts.addArguments("--no-sandbox");
                edgeOpts.addArguments("--window-size=1920,1080");
                return useGrid
                    ? new RemoteWebDriver(new URL(GRID_URL), edgeOpts)
                    : new EdgeDriver(edgeOpts);

            default:
                throw new IllegalArgumentException(
                    "Unsupported browser: " + browser
                    + ". Use chrome, firefox, or edge.");
        }
    }
}

BaseTest with ThreadLocal

When running parallel tests, each thread needs its own WebDriver. If two threads share one driver, chaos. ThreadLocal gives each thread its own isolated copy. This is non-negotiable for parallel execution.

base/BaseTest.javajava

import org.openqa.selenium.WebDriver;
import org.testng.annotations.*;

public class BaseTest {

    // Each thread gets its own driver — no interference
    protected static ThreadLocal<WebDriver> driverThread =
        new ThreadLocal<>();

    @Parameters({"browser"})
    @BeforeMethod
    public void setUp(
        @Optional("chrome") String browser) throws Exception {

        WebDriver driver = WebDriverFactory.createDriver(browser);
        driverThread.set(driver);
        driver.manage().window().maximize();
    }

    protected WebDriver getDriver() {
        return driverThread.get();
    }

    @AfterMethod
    public void tearDown() {
        WebDriver driver = driverThread.get();
        if (driver != null) {
            driver.quit();
            driverThread.remove(); // Prevent memory leaks
        }
    }
}

TestNG XML for Cross-Browser Execution

testng-crossbrowser.xmlxml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd">
<suite name="Cross-Browser Suite" parallel="tests" thread-count="3">

    <test name="Chrome Tests">
        <parameter name="browser" value="chrome" />
        <classes>
            <class name="com.practice.tests.LoginTest" />
            <class name="com.practice.tests.DashboardTest" />
        </classes>
    </test>

    <test name="Firefox Tests">
        <parameter name="browser" value="firefox" />
        <classes>
            <class name="com.practice.tests.LoginTest" />
            <class name="com.practice.tests.DashboardTest" />
        </classes>
    </test>

    <test name="Edge Tests">
        <parameter name="browser" value="edge" />
        <classes>
            <class name="com.practice.tests.LoginTest" />
            <class name="com.practice.tests.DashboardTest" />
        </classes>
    </test>

</suite>

Running It All Together

Run Cross-Browser Tests on Grid

Start Docker Grid: docker compose -f docker-compose-grid.yml up -d
Verify Grid is up: open http://localhost:4444/ui — all nodes should be green
Run tests on Grid: mvn clean test -DsuiteXmlFile=testng-crossbrowser.xml -Dgrid.url=http://localhost:4444
Watch the dashboard — sessions appear as tests start on each browser
Check test results — all 3 browsers run simultaneously, total time = time of slowest browser

If you use a regular WebDriver field instead of ThreadLocal, parallel tests will fight over the same browser instance. You'll get random NullPointerExceptions, wrong pages, and tests that pass/fail randomly. ThreadLocal is mandatory.

The @Optional("chrome") annotation means if you run a test without the TestNG XML (like directly from IntelliJ), it defaults to Chrome. No XML needed for local development.

Key Point: WebDriver Factory + ThreadLocal + TestNG parallel XML = same tests running on Chrome, Firefox, and Edge simultaneously on Grid.

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Chapter 4: Cross-Browser & Cloud Testing