JUnit assertArrayEquals Example

In this tutorial, we will learn how to write a JUnit test case to check two array objects are equal using the assertArrayEquals() static method.
The assertArrayEquals() method asserts that two object arrays are equal. If they are not, an AssertionError is thrown. If expected and actual are null, they are considered equal.

Let's first create Book, BookService classes, and then we will write JUnit test cases to use the assertArrayEquals() method.

Create Book Class

package junit5.bookstore.model;

public class Book {
	
	private String bookId;
	private String title;
	private String publisher;
	
	public Book(String bookId, String title, String publisher) {
		this.bookId = bookId;
		this.title = title;
		this.publisher = publisher;
	}

	public String getBookId() {
		return bookId;
	}

	public void setBookId(String bookId) {
		this.bookId = bookId;
	}

	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public String getPublisher() {
		return publisher;
	}

	public void setPublisher(String publisher) {
		this.publisher = publisher;
	}
	
}

Create BookService Class

package junit5.bookstore.service;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import junit5.bookstore.model.Book;

public class BookService {
	
	private List<Book> listOfBooks = new ArrayList<>();
	
	public void addBook(Book book) {
		listOfBooks.add(book);
	}	
	
	public List<Book> books(){
		return Collections.unmodifiableList(listOfBooks);
	}
	
	public Book getBookById(String bookId) {
		for(Book book : listOfBooks) {
			if(bookId.equals(book.getBookId())) {
				return book;
			}
		}
		return null;
	}
	
	public String[] getBookIdsByPublisher(String publisher) {
		List<String> bookIds = new ArrayList<>();
		for(Book book : listOfBooks) {
			if(publisher.equals(book.getPublisher())) {
				bookIds.add(book.getBookId());
			}
		}
		return bookIds.toArray(new String[bookIds.size()]);
	}
	
	public List<String> getBookTitlesByPublisher(String publisher) {
		List<String> bookTitles = new ArrayList<>();
		for(Book book : listOfBooks) {
			if(publisher.equals(book.getPublisher())) {
				bookTitles.add(book.getTitle());
			}
		}
		return bookTitles;
	}
}

Write JUnit test to use assertArrayEquals() method

The below Java program demonstrates the usage of all overloaded assertArrayEquals() static method:
package junit5.assertions.assertArraysEquals;

import static org.junit.jupiter.api.Assertions.assertArrayEquals;

import org.junit.jupiter.api.Test;

import junit5.bookstore.model.Book;
import junit5.bookstore.service.BookService;

public class AssertArraysEqualsDemo {
	
	@Test
	public void assertArrayEqualsWithNoMessage() {
		BookService bookService = new BookService();
		
		Book headFirstJavaBook = new Book("1", "Head First Java", "Wrox");
		Book headFirstDesignPatternBook = new Book("2", "Head First Design Pattern", "Packt");
		Book headFirstJavascriptBook = new Book("3", "Head First Javascript", "Wrox");
		
		bookService.addBook(headFirstJavaBook);
		bookService.addBook(headFirstDesignPatternBook);
		bookService.addBook(headFirstJavascriptBook);
		
		String[] actualBookIds = bookService.getBookIdsByPublisher("Wrox");
		
		assertArrayEquals(new String[] {"1", "3"}, actualBookIds);
	}
	
	@Test
	public void assertArrayEqualsWithMessage() {
		BookService bookService = new BookService();
		
		Book headFirstJavaBook = new Book("1", "Head First Java", "Wrox");
		Book headFirstDesignPatternBook = new Book("2", "Head First Design Pattern", "Packt");
		Book headFirstJavascriptBook = new Book("3", "Head First Javascript", "Wrox");
		
		bookService.addBook(headFirstJavaBook);
		bookService.addBook(headFirstDesignPatternBook);
		bookService.addBook(headFirstJavascriptBook);
		
		String[] actualBookIds = bookService.getBookIdsByPublisher("Wrox");
		
		assertArrayEquals(new String[] {"1", "3"}, actualBookIds, "bookIds didnt match !");
	}
	
	@Test
	public void assertArrayEqualsWithMessageSupplier() {
		BookService bookService = new BookService();
		
		Book headFirstJavaBook = new Book("1", "Head First Java", "Wrox");
		Book headFirstDesignPatternBook = new Book("2", "Head First Design Pattern", "Packt");
		Book headFirstJavascriptBook = new Book("3", "Head First Javascript", "Wrox");
		
		bookService.addBook(headFirstJavaBook);
		bookService.addBook(headFirstDesignPatternBook);
		bookService.addBook(headFirstJavascriptBook);
		
		String[] actualBookIds = bookService.getBookIdsByPublisher("Wrox");
		
		assertArrayEquals(new String[] {"1", "3"}, actualBookIds, () -> "bookIds didnt match !");
	}
}

Run JUnit test Class

Run the JUnit test class to execute all the JUnit test cases and here is the output:

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