TestNG Listeners in Selenium WebDriver With Examples

There are different interfaces provided by Java that allow you to modify TestNG behavior. These interfaces are further known as TestNG Listeners in Selenium WebDriver. TestNG Listeners also allow you to customize the tests logs or report according to your project requirements. TestNG Listeners in Selenium WebDriver are modules that listen to certain events and keep track of test execution while performing some action at every stage of test execution.

This is a TestNG tutorial, where I will help you realize the different TestNG listeners with examples so you can use them proficiently the next time you plan to work with TestNG and Selenium.

TestNG Listeners in Selenium WebDriver can be implemented at two levels:

1. Class level: In this, you implement listeners for each particular class, no matter how many test cases it includes.
2. Suite level: In this, you implement listeners for a particular suite which includes several classes of test cases.

Types of TestNG Listeners in Selenium WebDriver

There are numerous TestNG listeners in Selenium WebDriver, some of them are used very frequently by the testing community and some are almost forgotten. In this TestNG tutorial, I will demonstrate the most popular TestNG listeners with examples, but, before that, let me quickly go through the various TestNG listeners in Selenium WebDriver.

1. ITestListener
2. IAnnotationTransformer
3. IInvokedMethodListener
4. ISuiteListener
5. IReporter
6. IConfigurable
7. IExecutionListener
8. IHookable
9. IMethodInterceptor
10. IConfigurationListener

Frequently Used TestNG Listeners With Examples

Now, in this TestNG tutorial, let’s us first look into the most popular and widely used TestNG listeners with examples.

1. ITestListener

ITestListener is the most adopted TestNG listener in Selenium WebDriver. It provides you with an easy to implement interface through a normal Java class, where the class overrides every method declared inside the ITestListener. By using this TestNG listener in Selenium WebDriver, you can change the default behaviour of your test by adding different events to the methods. It also defines a new way of logging or reporting.

The following are some methods provided by this interface:

• onStart: This method is invoked before any test method gets executed. This can be used to get the directory from where the tests are running.

• onFinish: This method is invoked after all tests methods gets executed. This can be used to store information of all the tests that were run.

• onTestStart: This method is invoked before any test methods are invoked. This can be used to indicate that the particular test method has been started.

• onTestSkipped: This method is invoked when each test method is skipped. This can be used to indicate that the particular test method has been skipped.

• onTestSuccess: This method is invoked when any test method succeeds. This can be used to indicate that the particular test method has successfully finished its execution.

• onTestFailure: This method is invoked when any test method fails. This can be used to indicate that the particular test method has failed. You can create an event for taking a screenshot which will show where the test has been failed.

• onTestFailedButWithinSuccessPercentage: This method is invoked each time the test method fails but is within the success percentage mentioned. To implement this method, we use two attributes as a parameter of test annotation in TestNG, i.e. successPercentage and invocationCount. The successPercentage takes the value of percentage of successful tests and invocationCount denotes the number of times that a particular test method executes. For example:  @Test(successPercentage=60, invocationCount=5). In this annotation, the success percentage is 60% and the invocation count is 5, which means that out of 5 times, if the test method gets passed at least 3 times ((⅗)*100= 60), it will be considered as passed.

For every ITestListener method we usually pass the following arguments:

• “ITestResult” interface along with its instance, “result,” which describes the result of a test. Note: If you want to trace your exception through ITestResult then you need to avoid try/catch handling.
• “ITestContext” interface along with its instance “context” which describes the test context containing all the information of the given test run.

Now, in this TestNG tutorial for listeners, we will take a basic example code for running the test at the class level. Logs will get generated in the console and it will help you to understand which tests passed, failed, and got skipped. The first class (ListentersBlog.java) will contain all the methods implemented by the ITestListener interface:

package TestNgListeners;
import org.testng.ITestContext;
import org.testng.ITestListener;
import org.testng.ITestResult;
public class ListenersBlog implements ITestListener {
    public void onTestStart(ITestResult result) {
        System.out.println("New Test Started" + result.getName());
    }
    public void onTestSuccess(ITestResult result) {
        System.out.println("Test Successfully Finished" + result.getName());
    }
    public void onTestFailure(ITestResult result) {
        System.out.println("Test Failed" + result.getName());
    }
    public void onTestSkipped(ITestResult result) {
        System.out.println("Test Skipped" + result.getName());
    }
    public void onTestFailedButWithinSuccessPercentage(ITestResult result) {
        System.out.println("Test Failed but within success percentage" + result.getName());
    }
    public void onStart(ITestContext context) {
        System.out.println("This is onStart method" + context.getOutputDirectory());
    }
    public void onFinish(ITestContext context) {
        System.out.println("This is onFinish method" + context.getPassedTests());
        System.out.println("This is onFinish method" + context.getFailedTests());
    }
}

Below is the code that includes the tests methods (TestNGListenersTest.java). Make sure you add a Listeners annotation just above your class name to implement the above added methods. Syntax:  @Listeners(PackageName.ClassName.class)

package TestNgListeners;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.SkipException;
import org.testng.annotations.Listeners;
import org.testng.annotations.Test;
import junit.framework.Assert;
@Listeners(TestNgListeners.ListenersBlog.class) public class TestNGListenersTest {
    @Test //Passing Test public void sampleTest1() throws InterruptedException { 
    System.setProperty("webdriver.chrome.driver", "C:\\Users\\Lenovo-I7\\Desktop\\Selenium\\chromedriver.exe");
    WebDriver driver = new ChromeDriver();
    driver.get("https://www.apple.com/");
    driver.manage().window().maximize();
    driver.findElement(By.xpath("//*[@id=\'ac-globalnav\']/div/ul[2]/li[3]")).click();
    Thread.sleep(2000);
    driver.findElement(By.cssSelector("#chapternav > div > ul > li.chapternav-item.chapternav-item-ipad-air > a")).click();
    Thread.sleep(2000);
    driver.findElement(By.linkText("Why iPad")).click();
    Thread.sleep(2000);
    driver.quit();
}
@Test //Failing Test public void sampleTest2() throws InterruptedException { 
System.out.println("Forcely Failed Test Method");
Assert.assertTrue(false);
}
private int i = 0;
@Test(successPercentage = 60, invocationCount = 5) //Test Failing But Within Success Percentage public void sampleTest3() { i++; 
System.out.println("Test Failed But Within Success Percentage Test Method, invocation count: " + i); 
if (i == 1 || i == 2) { System.out.println("sampleTest3 Failed"); Assert.assertEquals(i, 6); } } 
@Test  //Skipping Test public void sampleTest4() { throw new SkipException("Forcely skipping the sampleTest4"); }   }

Console Output Screen: Now, suppose you have multiple classes in your project, then adding TestNG Listeners in Selenium WebDriver to each class might be a pain. In such cases, you can create a test suite and add a Listeners tag to your suite (XML file) instead of adding Listeners to each class. Here is the example code (testng.xml) for running the test at the suite level :

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
    <suite name="TestNG Listeners Suite" parallel="false">
        <listeners>
            <listener class-name="TestNgListeners.ListenersBlog" /> </listeners>
        <test name="Test">
            <classes>
                <class name="TestNgListeners.TestNGListenersTest" /> </classes>
        </test>
    </suite>

2. IAnnotationTransformer

IAnnotationTransformer is an interface that provides a “transform” method which gets invoked by TestNG to modify the behaviour of the test annotation method in our test class. The transform method provides various parameters:

1. annotation: The annotation that is read from the test class.
2. testClass: If the annotation found on a class, this parameter would represent that same class.
3. testConstructor: If the annotation found a constructor, this parameter would represent that same constructor.
4. testMethod: If the annotation found a method, this parameter would represent that same method.

Note: At least one of the parameters will be non-null.

Below is the sample code that would be executed at the suite level. In this code, we have used a parameter (“alwaysRun = true”) in our Test annotation that indicates that the test method would always run even if the parameters on which the method depends fails. However, we would transform this behavior of our test method through IAnnotationTransformer Listener which won’t allow the particular test method to get executed.

Listeners Class File:

package TestNgListeners;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import org.testng.IAnnotationTransformer;
import org.testng.annotations.ITestAnnotation;
public class AnnotationTransformers implements IAnnotationTransformer {
    public boolean isTestRunning(ITestAnnotation ins) {
        if (ins.getAlwaysRun()) {
            return true;
        }
        return false;
    }
    public void transform(ITestAnnotation annotation, Class testClass, Constructor testConstructor, Method testMethod) {
        if (isTestRunning(annotation)) {
            annotation.setEnabled(false);
        }
    }
}

Test Class File:

package TestNgListeners;
import org.testng.annotations.Listeners;
import org.testng.annotations.Test;
public class AnnotationTransformerTests {
    @Test(alwaysRun = true) public void test1() {
        System.out.println("This is my first test whose behaviour would get changed while executing");
    }
    @Test public void test2() {
        System.out.println("This is my second test executing");
    }
}

Console Output Screen:

3. IInvokedMethodListener

This interface allows you to perform some action before and after a method has been executed. This listener gets invoked for configuration and test methods. This TestNG listener in Selenium WebDriver works the same as the ITestListerner and the ISuiteListerner. However, there is a difference that you should make a note of and that is that, in IInvokedMethodListener, it makes the call before and after every method.

There are two methods to be implemented:

beforeInvocation(): This method is invoked prior every method.

afterInvocation(): This method is invoked post every method.

Here is sample code for this listener, implemented at class level.

InvokedMethodListeners.java(includes listeners implemented methods) package TestNgListeners;
import org.testng.IInvokedMethod;
import org.testng.IInvokedMethodListener;
import org.testng.ITestResult;
public class InvokedMethodListeners implements IInvokedMethodListener {
    public void beforeInvocation(IInvokedMethod method, ITestResult testResult) {
        System.out.println("Before Invocation of: " + method.getTestMethod().getMethodName() + "of Class:" + testResult.getTestClass());
    }
    public void afterInvocation(IInvokedMethod method, ITestResult testResult) {
        System.out.println("After Invocation of: " + method.getTestMethod().getMethodName() + "of Class:" + testResult.getTestClass());
    }
}

File Name: InvokedMethodListenersTest.java (includes configuration and test methods)

package TestNgListeners;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Listeners;
import org.testng.annotations.Test;
@Listeners(value = InvokedMethodListeners.class) public class InvokedMethodListenersTest {
    @Test public void test1() {
        System.out.println("My first test");
    }
    @Test public void test2() {
        System.out.println("My second test");
    }
    @BeforeClass public void setUp() {
        System.out.println("Before Class method");
    }
    @AfterClass public void cleanUp() {
        System.out.println("After Class method");
    }
}

Console Output Screen:

4. ISuiteListener

This TestNG listener in Selenium WebDriver is implemented at a suite level called ISuiteListener. It has two methods:

• onStart: This method is invoked prior the test suite execution.

• onFinish: This method is invoked post the test suite execution.

This listener basically listens to the events that have occurred before and after the execution of the suite. If the parent suite further contains child suites then child suites are executed before running the parent suite.

Step 1: Implementing ISuiteListener with normal java class and adding the unimplemented methods.

Class: SuiteListeners

package TestNgListeners;
import org.testng.ISuite;
import org.testng.ISuiteListener;
public class SuiteListeners implements ISuiteListener {
    public void onStart(ISuite suite) {
        System.out.println("Suite executed onStart" + suite.getName());
    }
    public void onFinish(ISuite suite) {
        System.out.println("Suite executed onFinish" + suite.getName());
    }
}

Step 2: Creating two test classes to be added in two different child suites.

Class 1: SuiteListenersTests1

package TestNgListeners;
import org.testng.annotations.AfterSuite;
import org.testng.annotations.BeforeSuite;
import org.testng.annotations.Test;
public class SuiteListenersTests1 {
    @BeforeSuite public void test1() {
        System.out.println("BeforeSuite method in Suite1");
    }
    @Test public void test2() {
        System.out.println("Main Test method 1");
    }
    @AfterSuite public void test3() {
        System.out.println("AfterSuite method in Suite1");
    }
}

Class 2: SuiteListenersTests2

package TestNgListeners;
import org.testng.annotations.AfterSuite;
import org.testng.annotations.BeforeSuite;
import org.testng.annotations.Test;
public class SuiteListenersTests2 {
    @BeforeSuite public void test1() {
        System.out.println("BeforeSuite method in Suite2");
    }
    @Test public void test2() {
        System.out.println("Main Test method 2");
    }
    @AfterSuite public void test3() {
        System.out.println("AfterSuite method in Suite2");
    }
}

Step 3: Adding the test classes to the child suites.

Suite 1: Test Suite One.xml

<?xml version="1.0" encoding="UTF-8"?>
<suite name="Test Suite One">
    <test name="Test Method1">
        <classes>
            <class name="TestNgListeners.SuiteListenersTests1" />
        </classes>
    </test>
</suite>

Suite 2: Test Suite Two.xml

<?xml version="1.0" encoding="UTF-8"?>
<suite name="Test Suite Two">
    <test name="Test Method2">
        <classes>
            <class name="TestNgListeners.SuiteListenersTests2" />
        </classes>
    </test>
</suite>

Step 4: Creating a parent suite xml file that would combine other 2 defined suites along with the listeners class.

<?xml version="1.0" encoding="UTF-8"?>
<suite name="suiteListener">
    <listeners>
        <listener class-name="TestNgListeners.SuiteListeners"></listener>
    </listeners>
    <suite-files>
        <suite-file path="./Suite1.xml"></suite-file>
        <suite-file path="./Suite2.xml"></suite-file>
    </suite-files>
</suite>

Console Output Screen:

5. IReporter

This TestNG listener in Selenium WebDriver provides an interface which helps you to customize the test report generated by TestNG. It provides the generateReport method which gets invoked after the execution of all the suites. The method further contains three parameters:

1. xmlSuite: it provides you with a list of multiple suites presented in the testng xml file that goes under execution.
2. suites: This object represents a great deal of information about the classes, packages, test execution result, along with all the test methods. Basically, it represents detailed information around the suite after the final execution.
3. outputDirectory: contains the output folder path where the report gets generated.

Below is the example of IReporterer listener at suite level.

File Name :ReporterListener.java

package TestNgListener;
import java.util.List;
import java.util.Map;
import org.testng.IReporter;
import org.testng.ISuite;
import org.testng.ISuiteResult;
import org.testng.ITestContext;
import org.testng.xml.XmlSuite;
public class ReporterListener implements IReporter {
    public void generateReport(List xmlSuites, List suites, String outputDirectory) {
        for (ISuite isuite: suites) {
            Map & lt;
            string, isuiteresult = "" & gt;
            suiteResults = isuite.getResults();
            String sn = isuite.getName();
            for (ISuiteResult obj: suiteResults.values()) {
                ITestContext tc = obj.getTestContext();
                System.out.println("Passed Tests of" + sn + "=" + tc.getPassedTests().getAllResults().size());
                System.out.println("Failed Tests of" + sn + "=" + tc.getFailedTests().getAllResults().size());
                System.out.println("Skipped Tests of" + sn + "=" + tc.getSkippedTests().getAllResults().size());
            }
        }
    }
} & lt;
/string,>

File Name: ReporterTest.java

package TestNgListener;
import org.testng.SkipException;
import org.testng.annotations.Listeners;
import org.testng.annotations.Test;
import junit.framework.Assert;
public class ReporterTest {
    @Test public void FirstTest() {
        System.out.println("The First Test Method");
        Assert.assertTrue(true);
    }
    @Test public void SecondTest() {
        System.out.println("The Second Test Method");
        Assert.fail("Failing this test case");
    }
    @Test public void ThirdTest() {
        System.out.println("The Third Test Method");
        throw new SkipException("Test Skipped");
    }
}

Console Output Screen:

Not So Frequently Used TestNG Listeners in Selenium WebDriver

In this section, I will be highlighting those TestNG listeners which are not so well known as the ones discussed in the previous section. I have avoided the practical demonstration of these TestNG listeners with their examples as they are rarely used. I will, however, help you understand their purpose.

6. IConfigurationListener

This TestNG listener in Selenium WebDriver is used to create an event only when the configuration method is passed, failed, or skipped. Below are the unimplemented methods provided by this listener:

• onConfigurationSuccess: It gets invoked when the configuration method succeeds.
• onConfigurationFailure: It gets invoked when the configuration method gets failed.
• onConfigurationSkip: As the name suggests, when your configuration method is skipped, it calls for the onConfigurationSkip method.

7. IExecutionListener

This listener is used to keep track of when the test or suite run started and finished. It provides two methods:

• onExecutionStart: It is invoked before the suite or test starts running.

• onExecutionFinish: It is invoked after the suite or test gets executed.

Note: It is not possible for this listener to prevent the execution but only to create events in some way. Also, you can provide more than one “IExecution” listener as you configure TestNG.

8. IHookable

This interface skips the invocation of test methods and provides a run method which gets invoked instead of each @Test method found. The test method is then invoked once the callBack() method of the IHookCallBack parameter is called.

The IHookable listener is utilized when you wish to perform testing on classes which require JAAS authentication. This can be used to set permissions, i.e. for whom the test method should run and when the test method should get skipped.

9. IMethodInterceptor

This method is used:

• to return the list of IMethodInstance, after the execution of TestNG.

• to sort the list of test methods.

TestNG executes the test methods in the same order defined in the returned value. The IMethodInterceptor interface includes only one method to implement “intercept,” which returns the modified list of test methods.

Example: One of the test methods SampleTestOne is to test the logs, so we grouped it in “LogCheck.”

Now, suppose we only want to run the LogCheck grouped tests and not the other tests, so, we have to provide an IMethodInterceptor listener that can eliminate the other tests and return only LogCheck grouped tests.

10. IConfigurable

The ICongurable listener is somewhat similar to the IHookable listener. This interface skips the invocation of test methods and provides a run method which gets invoked instead of each configuration method found. The configuration method is then invoked once the callBack() method of the IConfigureCallBack parameter is called.

Which TestNG Listeners in Selenium WebDriver Do You Use the Most?

I hope this TestNG tutorial, helped you to realize which TestNG listeners are most suitable for your project's requirements. Regarding the rarely used TestNG listeners, if there are any specific TestNG listeners in Selenium that you find highly useful then feel free to share them in the comments section below. Also, if you have any questions related to the article, let me know. I look forward to your replies. Happy testing!