TestNG provides an option of tracing the exception handling of code. You can test whether a code throws a desired exception or not. Here the expectedExceptions parameter is used along with the @Test annotation. Now, let”s see @Test(expectedExceptions) in action.

Create a Class

Create a java class to be tested, say, MessageUtil.java in /work/testng/src. Add an error condition inside the printMessage() method.

/*
* This class prints the given message on console.
*/
public class MessageUtil {

   private String message;

   //Constructor
   //@param message to be printed
   public MessageUtil(String message) {
      this.message = message;
   }

   // prints the message
   public void printMessage() {
      System.out.println(message);
      int a =0;
      int b = 1/a;
   }

   // add "Hi!" to the message
   public String salutationMessage() {
      message = "Hi!" + message;
      System.out.println(message);
      return message;
   }
}

Create Test Case Class

• Create a java test class, say, ExpectedExceptionTest.java in /work/testng/src.

• Add an expected exception ArithmeticException to the testPrintMessage() test case.

Following are the contents of ExpectedExceptionTest.java.

import org.testng.Assert;
import org.testng.annotations.Test;

public class ExpectedExceptionTest {
   String message = "Manisha";
   MessageUtil messageUtil = new MessageUtil(message);

   @Test(expectedExceptions = ArithmeticException.class)
   public void testPrintMessage() {
      System.out.println("Inside testPrintMessage()");
      messageUtil.printMessage();
   }

   @Test
   public void testSalutationMessage() {
      System.out.println("Inside testSalutationMessage()");
      message = "Hi!" + "Manisha";
      Assert.assertEquals(message,messageUtil.salutationMessage());
   }
}

Create Test Runner

Create testng.xml in /work/testng/src to execute test case(s).

<?xml version = "1.0" encoding = "UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd" >

<suite name = "Suite1">
   <test name = "test1">
      <classes>
         <class name = "ExpectedExceptionTest" />
      </classes>
   </test>
</suite>

Compile the MessageUtil, Test case classes using javac.

/work/testng/src$ javac MessageUtil.java TestJunit.java

Now, run the Test Runner, which will run test cases defined in the provided Test Case class.

/work/testng/src$ java org.testng.TestNG testng.xml

Verify the output. testPrintMessage() test case will be passed.

Inside testPrintMessage()
Manisha
Inside testSalutationMessage()
Hi!Manisha

===============================================
Suite1
Total tests run: 2, Failures: 0, Skips: 0
===============================================