Summary  
Demonstrates how to use assertThrows and assertDoesNotThrow assertions to verify that methods either throw the expected exceptions or complete without error.  

General domain of usage  
Unit testing

I hope you remember how you wrote exception handling in  <a 
href="https://codefinity.com/courses/v2/455bd504-41cd-4fd0-98b7-9f3ee575d21a/7425cfcb-65fa-4ed7-b6b5-510ed254606b/0d988351-450a-40d8-819b-8e5af0fae862"
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onmouseout="this.style.color='#d27204'">this</a> chapter. **It's time to practice** writing tests for these assertions.

# Task

Your task is to **cover two methods** from the `ExceptionHandlingExercise` class **with tests** using `assertThrows()` and `assertDoesNotThrow()` assertions in the **unit test class** that I have created for you.

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  <li>
    Pay attention to the <b>names of the unit tests</b>; your task is to
    implement them so that they
    <b>perform the function indicated in the name</b>.
  </li>
  <li>
    At the beginning of each test, you need to <b>create an instance</b> of the
    <code>ExceptionHandlingExercise</code> class. It will look like this:
    <br /><code
      >ExceptionHandlingExercise exercise = new
      ExceptionHandlingExercise();</code
    >.
  </li>
  <li>
    Next, you need to create a
    <b>variable that will hold the value you want to test</b>. <br />
    For example: <code>int underage = 17;</code>.
  </li>
  <li>Use the <b>assertions you learned</b> in the previous chapter.</li>
  <li>
    You can <b>optionally</b> write additional tests for the functionality of
    these methods.
  </li>
</div>

<div id="solution-block33" class="block solution-styling-block">
  
  <textarea id="code-33" class="language-java">
package codefinity;

import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
import org.junit.jupiter.api.Test;

public class ExceptionHandlingExerciseTest {

    @Test
    public void checkAge_ShouldThrowIllegalArgumentException_WhenAgeIsLessThan18() {
        ExceptionHandlingExercise exercise = new ExceptionHandlingExercise();
        int underage = 17;

        assertThrows(IllegalArgumentException.class, () -> {
            exercise.checkAge(underage);
        });
    }

    @Test
    public void checkAge_ShouldNotThrowException_WhenAgeIs18OrMore() {
        ExceptionHandlingExercise exercise = new ExceptionHandlingExercise();
        int legalAge = 18;

        assertDoesNotThrow(() -> {
            exercise.checkAge(legalAge);
        });
    }

    @Test
    public void printLength_ShouldThrowNullPointerException_WhenStringIsNull() {
        ExceptionHandlingExercise exercise = new ExceptionHandlingExercise();
        String nullString = null;

        assertThrows(NullPointerException.class, () -> {
            exercise.printLength(nullString);
        });
    }

    @Test
    public void printLength_ShouldNotThrowException_WhenStringIsNotNull() {
        ExceptionHandlingExercise exercise = new ExceptionHandlingExercise();
        String nonNullString = "JUnit";

        assertDoesNotThrow(() -> {
            exercise.printLength(nonNullString);
        });
    }
}</textarea
  >

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Testing is an integral part of software development. Every module of an application should be covered by tests to ensure the correctness of a specific module or the entire application. This course will teach you about the different types of application testing. Additionally, you will practice with unit tests to test individual components of your application.

Let's talk about types of testing and which testing methods developers use. You will learn about the stages an application goes through before being delivered to the client and the specific tests you will need to write.


In this section, we're going to dive into unit testing — you'll get the rundown on its structure in Java and the ins and outs of crafting them the right way. Setting up your IDE, importing necessary libraries, and lots of hands-on practice.


In this section, we will enhance our coding skills by dealing with errors that can also be caught in unit tests. When testing an application, you may come across various errors, and sometimes they should be turned into exceptions. I will explain how to catch exceptions in your code, test them, and handle them properly.

Testing Exceptions Practice

Task