TestNG listeners are interfaces that modifies the default testNG's behaviour. These are called when an event occurs in tests. ​

In testNG, below are the major types of listeners : ​

1. ITestListener

2. IReporter

3. IAnnotaionTransformer

4. IAnnotaionTransformer2

5. IConfigurableListener

6. IConfigurationListener

7. IExecutionListener

8. IHookable

9. IInvokedMethodListener

10. IInvokedMethodListener2

11. IMethodInterceptor

12. ISuiteListener

​

ITestListener is the most adopted listener above all. So, here we'll move forward with ITestListener. ​

Below are the methods of interface ITestListener :

public void onStart(ITestContext context) ​ public void onFinish(ITestContext context) ​ public void onTestStart(ITestResult result) public void onTestSuccess(ITestResult result) ​ public void onTestFailure(ITestResult result) ​ public void onTestSkipped(ITestResult result) ​ public void onTestFailedButWithinSuccessPercentage(ITestResult result) ​ ​

Listeners can be implemented at two levels :

• At Class Level

• At Suite Level

​

Implementeing listeners at class level To apply listeners on test classes, first create a listener class and implement the mentioned listener interface then override its methods. Now use '@Listeners' annotation before the test class and pass the .class name of the created listener class.

Syntax :

@Listeners(classname.class) ​ ​

Example :

package testNGexamples; import org.testng.ITestContext; import org.testng.ITestListener; import org.testng.ITestResult; public class ListenerClass implements ITestListener { ​ @Override public void onStart(ITestContext context) { System.out.println("Test Class Instantiated :"); } ​ @Override public void onFinish(ITestContext context) { System.out.println("All Tests Finished : :"); } ​ @Override public void onTestStart(ITestResult result) { System.out.println(result.getName() + "Test Method is Called :"); } ​ @Override public void onTestSuccess(ITestResult result) { System.out.println(result.getName() + "Test is Success :"); } ​ @Override public void onTestFailure(ITestResult result) { System.out.println(result.getName() + "Test Failed :"); } ​ @Override public void onTestSkipped(ITestResult result) { System.out.println(result.getName() + "Test skipped :"); } ​ @Override public void onTestFailedButWithinSuccessPercentage(ITestResult result) { System.out.println(result.getName() + "Test Failed But Within Succes Percentage :"); } } ​

Adding above class in test class using @Listeners annotation as :

package testNGexamples; import org.testng.Assert; import org.testng.SkipException; import org.testng.annotations.Listeners; import org.testng.annotations.Test; @Listeners(ListenerClass.class) public class TestNGWithListeners { int num = 1, i = 1; ​ @Test public void simpleFunction() { System.out.println("simpleFunction is Passed :"); } ​ @Test(successPercentage = 60, invocationCount = 2) public void repeatedTest() { Assert.assertEquals(num, i); num++; } ​ @Test public void testAssertCheck() { Assert.assertEquals(num, i); num++; } ​ @Test public void testSkip() { throw new SkipException("testSkip must be Skipped :"); } } ​

Output :

[RemoteTestNG] detected TestNG version 7.4.0 Test Class Instantiated : repeatedTestTest Method is Called : repeatedTestTest is Success : repeatedTestTest Method is Called : repeatedTestTest Failed But Within Succes Percentage : simpleFunctionTest Method is Called : simpleFunction is Passed : simpleFunctionTest is Success : testAssertCheckTest Method is Called : testAssertCheckTest Failed : testSkipTest Method is Called : testSkipTest skipped : All Tests Finished : : PASSED: simpleFunction PASSED: repeatedTest FAILED: testAssertCheck =============================================== Default test Tests run: 4, Failures: 1, Skips: 1 =============================================== =============================================== Default suite Total tests run: 5, Passes: 2, Failures: 2, Skips: 1 =============================================== ​ ​

Implementeing listeners at suite level To apply listeners at suite level, just remove @Listeners annotation from the class and add <listener> in .xml as : ​

<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd"> <suite name="Test-Suite"> <listeners> <listener class-name="testNGexamples.ListenerClass"></listener> </listeners> <test name="TestNG Listeners Execution"> <classes> <class name="testNGexamples.TestNGWithListeners"></class> </classes> </test> </suite> ​

Here 'ListenerClass' is the class in which interface methods have been overrided and 'TestNGWithListeners' is the class on which listener is applied. ​ ​ ​ ​ ​