To test that comments can be added, and to inspect the data element of the ArrayList object.

Explanation:

Java allows using the JUnit test framework to write and execute automated tests. It contains a set of assert methods to test method code. It uses @Test annotation to define the test case. It also includes two methods:

• setUp() method that runs before every test invocation.
• tearDown() method that runs after every test method.

Program:

The required Java code for JUnit test case is given below:

import static org.junit.Assert.*;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
// The test class SalesItemTest.
public class SalesItemTest
{
 // Default constructor 
 public SalesItemTest()
 {
 }
 // Sets up the test fixture.
 @Before
 public void setUp()
 {
 }
 // Tears down the test fixture.
 @After
 public void tearDown()
 {
 }
 /&
 * Test case to add two comments and that check the size of ArrayList is correct afterwards. 
 */
 @Test
 public void testAddComments()
 {
 SalesItem salesItem1 = new SalesItem("Java for complete Idiots", 21998);
 assertEquals(true, salesItem1.addComment("James Duckling", "This book is great.", 4));
 assertEquals(true, salesItem1.addComment("Jhoky Jonathan", "Super Java book.", 5));
 assertEquals(2, salesItem1.getNumberOfComments());
 }
}

In the above JUnit test case, the two comments are added then test the size of ArrayList by comparing the return value of getNumberOfComments() method with 2.

Objects First with Java: A Practical Introduction Using BlueJ (6th Edition), Chapter 9, Problem 1E , additional homework tip 1

The inspector to check for the comment list, their size, and elementData field of ArrayList object is as follows:

Objects First with Java: A Practical Introduction Using BlueJ (6th Edition), Chapter 9, Problem 1E , additional homework tip 2