Testing Thrown Exceptions in JUnit

In software development, exception handling is a crucial aspect that ensures that a system can recover from unexpected events. It is imperative to test the exception-throwing behavior of the code to ensure that the system can handle such events correctly. In this blog post, we will discuss the various methods to test thrown exceptions in JUnit, a widely used testing framework for Java applications.

1. Using the @Test and expected Attribute

The simplest way to test thrown exceptions in JUnit is to use the @Test and expected attributes. The expected attribute specifies the type of exception that the test method is expected to throw. If the test method throws an exception of the specified type, the test passes. If not, the test fails.

Here’s an example:

import org.junit.Test;

public class ExceptionTest {
    @Test(expected = ArithmeticException.class)
    public void divideByZero() {
        int a = 1 / 0;
    }
}

In this example, the divideByZero method is expected to throw an ArithmeticException, and the test will pass if the exception is thrown.

2. Using the try-catch Block

Another method to test thrown exceptions in JUnit is to use a try-catch block. In this method, the test code is enclosed in a try block, and the expected exception is caught in a catch block. After catching the exception, you can use JUnit's assert methods to verify that the exception was thrown as expected.