Parallel execution configuration in Selenium Java - Build an Automation Script

Configure and run Selenium tests in parallel using TestNG

Preconditions (2)

Step 1: Create a TestNG XML suite file with parallel execution enabled

Step 2: Set parallel attribute to 'tests' and thread-count to 2 in the suite tag

Step 3: Include LoginTest and SearchTest classes as separate test tags in the suite

Step 4: Run the TestNG suite XML file

Step 5: Observe that LoginTest and SearchTest run at the same time in separate threads

✅ Expected Result: Both LoginTest and SearchTest execute simultaneously without waiting for each other, completing successfully.

Automation Requirements - TestNG with Selenium WebDriver

Assertions Needed:

Verify both test classes complete successfully

Verify tests run in parallel threads (thread IDs differ)

Best Practices:

Use TestNG XML suite file to configure parallel execution

Avoid sharing WebDriver instances between tests

Use thread-safe WebDriver initialization

Use explicit waits instead of Thread.sleep

Automated Solution

Selenium Java

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.Assert;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;

public class LoginTest {
    private WebDriver driver;

    @BeforeMethod
    public void setUp() {
        driver = new ChromeDriver();
    }

    @Test
    public void testLogin() {
        driver.get("https://example.com/login");
        String threadName = Thread.currentThread().getName();
        System.out.println("LoginTest running on thread: " + threadName);
        Assert.assertEquals(driver.getTitle(), "Login Page");
    }

    @AfterMethod
    public void tearDown() {
        if (driver != null) {
            driver.quit();
        }
    }
}

// Another test class
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.Assert;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;

public class SearchTest {
    private WebDriver driver;

    @BeforeMethod
    public void setUp() {
        driver = new ChromeDriver();
    }

    @Test
    public void testSearch() {
        driver.get("https://example.com/search");
        String threadName = Thread.currentThread().getName();
        System.out.println("SearchTest running on thread: " + threadName);
        Assert.assertTrue(driver.getTitle().contains("Search"));
    }

    @AfterMethod
    public void tearDown() {
        if (driver != null) {
            driver.quit();
        }
    }
}

/* TestNG XML suite file (testng.xml):
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd">
<suite name="ParallelSuite" parallel="tests" thread-count="2">
  <test name="LoginTest">
    <classes>
      <class name="LoginTest"/>
    </classes>
  </test>
  <test name="SearchTest">
    <classes>
      <class name="SearchTest"/>
    </classes>
  </test>
</suite>
*/

The solution includes two separate test classes: LoginTest and SearchTest. Each class creates its own WebDriver instance in the @BeforeMethod and closes it in @AfterMethod to avoid sharing drivers between threads.

The TestNG XML suite file configures parallel execution by setting parallel="tests" and thread-count="2". This means TestNG will run the two test classes at the same time in separate threads.

Inside each test, we print the current thread name to the console to confirm parallel execution. Assertions check the page titles to verify the tests run correctly.

This setup follows best practices by isolating WebDriver instances per test and using TestNG's built-in parallel execution features.

Common Mistakes - 4 Pitfalls

Sharing a single WebDriver instance across multiple tests

Using Thread.sleep instead of explicit waits

{'mistake': 'Not configuring parallel attribute in TestNG XML', 'why_bad': 'Tests will run sequentially, not in parallel as intended.', 'correct_approach': 'Set parallel="tests" and thread-count in the TestNG suite XML.'}

Using hardcoded XPath locators that are brittle

Bonus Challenge

Now add data-driven testing to LoginTest with 3 different username and password combinations

Show Hint