Selenium TestNG Framework Tutorial: Annotations, Assertions and Test Execution

 

Introduction

Selenium WebDriver is a popular tool for automating web applications. However, Selenium alone does not provide a complete test management framework for organising, executing and reporting automated test cases.

This is where TestNG becomes useful.

TestNG is a Java testing framework inspired by JUnit and NUnit. It provides features such as annotations, assertions, test prioritisation, grouping, parameterisation, dependencies and parallel execution.

When combined with Selenium WebDriver, TestNG helps automation testers build structured, maintainable and reusable test automation suites.

In this tutorial, we will understand TestNG concepts and learn how to integrate TestNG with Selenium using practical Java examples.

1. What Is TestNG?

TestNG stands for Test Next Generation. It is a testing framework designed to simplify test organisation and execution.

It is commonly used in Selenium automation projects to:

• Organise test cases.

• Control test execution order.

• Run tests in groups.

• Validate expected and actual results.

• Execute tests with different data sets.

• Support parallel execution.

• Generate execution reports.

TestNG is particularly useful when developing a Selenium automation framework for a real-world application.

2. Installing TestNG in a Selenium Java Project

You can use TestNG with Eclipse and Maven.

Step 1: Create a Maven Project

Open Eclipse and create a new Maven project.

Step 2: Add Dependencies

Add Selenium and TestNG dependencies to your pom.xml file.

<dependencies>

    <dependency>
        <groupId>org.seleniumhq.selenium</groupId>
        <artifactId>selenium-java</artifactId>
        <version>4.38.0</version>
    </dependency>

    <dependency>
        <groupId>org.testng</groupId>
        <artifactId>testng</artifactId>
        <version>7.11.0</version>
        <scope>test</scope>
    </dependency>

</dependencies>

These are example dependency versions. Use compatible current versions when setting up a new project.

Step 3: Install the TestNG Eclipse Plugin

In Eclipse:

1. Open the Eclipse Marketplace.

2. Search for TestNG.

3. Install the TestNG plugin.

4. Restart Eclipse if prompted.

You can also execute TestNG tests through Maven without relying on the Eclipse plugin.

3. Understanding TestNG Annotations

Annotations are one of the most important features of TestNG. They control when different test methods and configuration methods execute.

Common TestNG annotations include:

Annotation	Purpose
@BeforeSuite	Runs before the test suite
@AfterSuite	Runs after the test suite
@BeforeTest	Runs before the relevant XML test
@AfterTest	Runs after the relevant XML test
@BeforeClass	Runs before the first test method in a class
@AfterClass	Runs after all test methods in a class
@BeforeMethod	Runs before each test method
@AfterMethod	Runs after each test method
@Test	Marks a test method

Example of TestNG Annotations

import org.testng.annotations.*;

public class AnnotationExample {

    @BeforeSuite
    public void beforeSuite() {
        System.out.println("Before Suite");
    }

    @BeforeClass
    public void beforeClass() {
        System.out.println("Before Class");
    }

    @BeforeMethod
    public void beforeMethod() {
        System.out.println("Before Test Method");
    }

    @Test
    public void testLogin() {
        System.out.println("Executing Login Test");
    }

    @AfterMethod
    public void afterMethod() {
        System.out.println("After Test Method");
    }

    @AfterClass
    public void afterClass() {
        System.out.println("After Class");
    }

    @AfterSuite
    public void afterSuite() {
        System.out.println("After Suite");
    }
}

The annotations help testers control test setup, execution and cleanup.

4. Writing a Selenium TestNG Test Case

Let us create a simple Selenium test that opens a webpage and verifies its title.

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.Assert;
import org.testng.annotations.*;

public class SeleniumTestNGExample {

    WebDriver driver;

    @BeforeMethod
    public void setUp() {
        driver = new ChromeDriver();
        driver.get("https://example.com");
    }

    @Test
    public void verifyPageTitle() {

        String actualTitle = driver.getTitle();

        Assert.assertEquals(
            actualTitle,
            "Example Domain"
        );
    }

    @AfterMethod(alwaysRun = true)
    public void tearDown() {

        if (driver != null) {
            driver.quit();
        }
    }
}

In this example:

• @BeforeMethod launches the browser and opens the webpage.

• @Test executes the validation.

• Assert.assertEquals() compares the actual and expected page titles.

• @AfterMethod closes the browser even if the test fails.

5. TestNG Assertions

Assertions are used to verify whether an application behaves as expected.

TestNG provides several assertion methods.

Assert Equals

Assert.assertEquals(actual, expected);

Checks whether two values are equal.

Assert True

Assert.assertTrue(driver.getTitle().contains("Example"));

Checks whether a condition is true.

Assert False

Assert.assertFalse(driver.getTitle().contains("Error"));

Checks whether a condition is false.

Assert Not Null

Assert.assertNotNull(driver);

Checks whether an object is not null.

Hard Assertions and Soft Assertions

A hard assertion stops the current test method when an assertion fails.

Soft assertions allow execution to continue after an assertion failure. The tester must call assertAll() to report accumulated failures.

import org.testng.asserts.SoftAssert;

SoftAssert softAssert = new SoftAssert();

softAssert.assertEquals(actualTitle, expectedTitle);
softAssert.assertTrue(driver.getCurrentUrl().contains("example"));

softAssert.assertAll();

6. TestNG Priority

TestNG allows test methods to be assigned priorities.

@Test(priority = 1)
public void loginTest() {
    System.out.println("Login Test");
}

@Test(priority = 2)
public void dashboardTest() {
    System.out.println("Dashboard Test");
}

@Test(priority = 3)
public void logoutTest() {
    System.out.println("Logout Test");
}

Lower numeric priorities execute before higher numeric priorities under normal TestNG execution.

However, priority should not be used as a substitute for proper test independence or dependency management.

7. TestNG Groups

Groups allow related test cases to be organised and executed together.

@Test(groups = {"smoke"})
public void loginTest() {
    System.out.println("Smoke Test");
}

@Test(groups = {"regression"})
public void paymentTest() {
    System.out.println("Regression Test");
}

You can select groups for execution through a TestNG XML configuration file.

8. TestNG XML Configuration

A TestNG XML file helps control which test classes, methods or groups should execute.

Example testng.xml:

<!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd">

<suite name="AutomationSuite">

    <test name="LoginTests">

        <classes>
            <class name="SeleniumTestNGExample"/>
        </classes>

    </test>

</suite>

You can run this configuration as a TestNG Suite from Eclipse or through a compatible Maven TestNG setup.

9. TestNG Parameterisation

Parameterisation allows the same test method to execute with different input values.

TestNG supports parameters through @Parameters and data-driven execution through @DataProvider.

Using DataProvider

@DataProvider(name = "loginData")
public Object[][] getLoginData() {

    return new Object[][] {
        {"user1", "pass1"},
        {"user2", "pass2"},
        {"user3", "pass3"}
    };
}

@Test(dataProvider = "loginData")
public void loginTest(String username, String password) {

    System.out.println(username);
    System.out.println(password);
}

This approach is useful for testing login functionality with multiple combinations of credentials.

10. Parallel Execution in TestNG

TestNG supports parallel execution through XML configuration.

Example:

<suite name="ParallelSuite" parallel="methods" thread-count="3">

    <test name="AutomationTests">
        <classes>
            <class name="SeleniumTestNGExample"/>
        </classes>
    </test>

</suite>

Parallel execution can reduce overall test duration. However, Selenium tests must use properly isolated WebDriver instances, commonly through ThreadLocal or another safe driver-management approach, to avoid browser-session conflicts.

11. TestNG Reports

TestNG generates execution reports after running tests.

Common output files include:

• test-output/index.html

• test-output/emailable-report.html

These reports help testers review:

• Passed test cases.

• Failed test cases.

• Skipped tests.

• Execution details.

• Error information.

For larger automation projects, TestNG reports can also be integrated with reporting tools such as Allure or Extent Reports.

12. Best Practices for Selenium TestNG Frameworks

1. Keep test methods focused on one validation objective.

2. Use meaningful test method names.

3. Separate browser setup and cleanup from test logic.

4. Use assertions to validate actual application behaviour.

5. Use DataProviders for multiple test inputs.

6. Organise smoke and regression tests into groups.

7. Avoid unnecessary dependencies between test cases.

8. Use isolated WebDriver instances for parallel execution.

9. Maintain reusable methods and Page Object Model classes.

10. Integrate automated execution with CI/CD pipelines.

Frequently Asked Questions

1. What is TestNG in Selenium?

TestNG is a Java testing framework used with Selenium WebDriver to organise, execute and report automated test cases.

2. What are the most important TestNG annotations?

Common annotations include @Test, @BeforeMethod, @AfterMethod, @BeforeClass, @AfterClass, @BeforeSuite and @AfterSuite.

3. What is the difference between hard and soft assertions?

Hard assertions stop the current test method after a failure. Soft assertions collect failures and report them when assertAll() is called.

4. What is DataProvider in TestNG?

@DataProvider supplies multiple sets of test data to a test method.

5. Can TestNG execute Selenium tests in parallel?

Yes. TestNG supports parallel execution at suite, test, class and method levels, provided the automation framework manages browser sessions safely.

6. Is TestNG required for Selenium?

No. Selenium can be used with other test frameworks, but TestNG is a popular choice for Java-based automation projects.

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