package com.example;

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

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

public class MainTest {
    Library library;
    Book book1;
    Book book2;
    Book book3;

    @BeforeEach
    void setup() {
        library = new Library();
        book1 = new Book(1, "1984", "George Orwell");
        book2 = new Book(2, "Brave New World", "Aldous Huxley");
        book3 = new Book(3, "Fahrenheit 451", "Ray Bradbury");
    }

    @Test
    @DisplayName("addBook() adds a book to the library")
    void testAddBook() throws Exception {
        library.addBook(book1);
        List<Book> books = getBooksList();
        assertEquals(1, books.size(), "addBook should add one book to the collection");
        assertSame(book1, books.get(0), "The added book should be present in the list");
    }

    @Test
    @DisplayName("addBook() adds multiple books and preserves order")
    void testAddMultipleBooks() throws Exception {
        library.addBook(book1);
        library.addBook(book2);
        library.addBook(book3);
        List<Book> books = getBooksList();
        assertEquals(3, books.size(), "Should have three books after three adds");
        assertSame(book2, books.get(1), "Second book should be book2");
    }

    @Test
    @DisplayName("findBooksByAuthor() returns correct books (single match)")
    void testFindBooksByAuthorSingleMatch() throws Exception {
        library.addBook(book1);
        library.addBook(book2);
        List<Book> found = library.findBooksByAuthor("George Orwell");
        assertEquals(1, found.size(), "Should find one book by George Orwell");
        assertSame(book1, found.get(0), "Should return the correct book instance");
    }

    @Test
    @DisplayName("findBooksByAuthor() returns correct books (multiple matches)")
    void testFindBooksByAuthorMultipleMatches() throws Exception {
        Book anotherOrwell = new Book(4, "Animal Farm", "George Orwell");
        library.addBook(book1);
        library.addBook(anotherOrwell);
        library.addBook(book3);
        List<Book> found = library.findBooksByAuthor("George Orwell");
        assertEquals(2, found.size(), "Should find two books by George Orwell");
        assertTrue(found.contains(book1) && found.contains(anotherOrwell), "Both Orwell books should be in the result");
    }

    @Test
    @DisplayName("findBooksByAuthor() returns empty list when no matches")
    void testFindBooksByAuthorNoMatch() throws Exception {
        library.addBook(book2);
        library.addBook(book3);
        List<Book> found = library.findBooksByAuthor("George Orwell");
        assertNotNull(found, "Should not return null");
        assertEquals(0, found.size(), "Should return empty list if no matches");
    }

    @Test
    @DisplayName("findBooksByAuthor() is case-sensitive")
    void testFindBooksByAuthorCaseSensitive() throws Exception {
        library.addBook(book1);
        List<Book> found = library.findBooksByAuthor("george orwell");
        assertEquals(0, found.size(), "Should return empty list for case mismatch");
    }

    @Test
    @DisplayName("displayAllBooks() prints all books in the correct format and order")
    void testDisplayAllBooksPrintsCorrectly() throws Exception {
        library.addBook(book1);
        library.addBook(book2);
        library.addBook(book3);
    
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));
    
        library.displayAllBooks();
    
        System.setOut(originalOut);
    
        String output = outContent.toString().trim();
        String[] lines = output.split("\\r?\\n");
    
        assertEquals(3, lines.length, "displayAllBooks should print one line per book");
    
        assertTrue(
            lines[0].contains("ID: 1") && lines[0].contains("1984") && lines[0].contains("George Orwell"),
            "First line should contain book1 details"
        );
        assertTrue(
            lines[1].contains("ID: 2") && lines[1].contains("Brave New World") && lines[1].contains("Aldous Huxley"),
            "Second line should contain book2 details"
        );
        assertTrue(
            lines[2].contains("ID: 3") && lines[2].contains("Fahrenheit 451") && lines[2].contains("Ray Bradbury"),
            "Third line should contain book3 details"
        );
    }

    
    // Helper method to access private books list
    @SuppressWarnings("unchecked")
    private List<Book> getBooksList() throws Exception {
        Field booksField = Library.class.getDeclaredField("books");
        booksField.setAccessible(true);
        return (List<Book>) booksField.get(library);
    }
}

MainTest.java

A hands-on guide to Java data structures and collections. Explore lists, linked lists, queues, deques, stacks, and maps, while practicing CRUD operations, algorithmic complexity, and real-world challenges like library management and browser history.

Challenge: Library Management System

Solution

Challenge: Library Management System

Solution