Test parallelization in CI in Selenium Java - Test Execution Trace

Test Overview

This test runs two simple Selenium tests in parallel using TestNG in a Continuous Integration (CI) environment. It verifies that both tests execute independently and pass without interference.

Test Code - TestNG

Selenium Java

import org.openqa.selenium.By;
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 ParallelTest {
    private WebDriver driver;

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

    @Test(timeOut = 10000)
    public void testGoogleTitle() {
        driver.get("https://www.google.com");
        String title = driver.getTitle();
        Assert.assertEquals(title, "Google");
    }

    @Test(timeOut = 10000)
    public void testBingTitle() {
        driver.get("https://www.bing.com");
        String title = driver.getTitle();
        Assert.assertEquals(title, "Bing");
    }

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

Execution Trace - 10 Steps

Step	Action	System State	Assertion	Result
1	TestNG starts test suite with parallel execution enabled	TestNG initializes two test methods to run in parallel threads	-	PASS
2	First thread runs testGoogleTitle: opens Chrome browser	Chrome browser instance 1 opens at blank page	-	PASS
3	Second thread runs testBingTitle: opens Chrome browser	Chrome browser instance 2 opens at blank page	-	PASS
4	First thread navigates to https://www.google.com	Browser instance 1 shows Google homepage	Page title is 'Google'	PASS
5	Second thread navigates to https://www.bing.com	Browser instance 2 shows Bing homepage	Page title is 'Bing'	PASS
6	First thread asserts page title equals 'Google'	Title retrieved from browser instance 1	Assert.assertEquals(title, "Google")	PASS
7	Second thread asserts page title equals 'Bing'	Title retrieved from browser instance 2	Assert.assertEquals(title, "Bing")	PASS
8	First thread closes browser instance 1	Browser instance 1 closed	-	PASS
9	Second thread closes browser instance 2	Browser instance 2 closed	-	PASS
10	TestNG completes all parallel test executions	All tests finished with no failures	All assertions passed	PASS

Failure Scenario

Failing Condition: If the browser driver is not thread-safe or shared incorrectly, tests interfere causing wrong page titles or exceptions

Execution Trace Quiz - 3 Questions

What ensures that the two tests run at the same time in this TestNG setup?

A Calling driver.get() twice in the same test

B Enabling parallel="methods" with thread-count="2" in TestNG suite configuration

C Using @BeforeMethod and @AfterMethod annotations

D Running tests sequentially in one thread

Key Result

Always create and quit a separate WebDriver instance per test method when running tests in parallel to avoid conflicts and ensure reliable results.