package com.example;

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

public class MainTest {
    @Test
    @DisplayName("size() returns 0 for empty list")
    void testEmptyListSize() {
        LinkedList list = new LinkedList();
        assertEquals(0, list.size(), "size() should return 0 for an empty list");
    }

    @Test
    @DisplayName("size() returns correct count after adds")
    void testSizeAfterAdd() {
        LinkedList list = new LinkedList();
        list.add(1);
        list.add(2);
        list.add(3);
        assertEquals(3, list.size(), "size() should return 3 after adding 3 elements");
    }

    @Test
    @DisplayName("delete() removes head element and size updates")
    void testDeleteHead() {
        LinkedList list = new LinkedList();
        list.add(7);
        list.add(8);
        list.add(9);
        list.delete(0);
        assertEquals(2, list.size(), "size() should return 2 after deleting head");
        assertEquals(8, list.get(0), "First element should now be 8");
    }

    @Test
    @DisplayName("delete() removes middle element and size updates")
    void testDeleteMiddle() {
        LinkedList list = new LinkedList();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.delete(2); // Removes 3
        assertEquals(3, list.size(), "size() should return 3 after deleting index 2");
        assertEquals(4, list.get(2), "Element at index 2 should now be 4");
    }

    @Test
    @DisplayName("delete() removes last element and size updates")
    void testDeleteLast() {
        LinkedList list = new LinkedList();
        list.add(5);
        list.add(6);
        list.add(7);
        list.delete(2);
        assertEquals(2, list.size(), "size() should return 2 after deleting last element");
        assertThrows(IndexOutOfBoundsException.class, () -> list.get(2), "Accessing deleted index should throw");
    }

    @Test
    @DisplayName("delete() throws IndexOutOfBoundsException for invalid index")
    void testDeleteInvalidIndex() {
        LinkedList list = new LinkedList();
        list.add(1);
        list.add(2);
        assertThrows(IndexOutOfBoundsException.class, () -> list.delete(-1), "Negative index should throw");
        assertThrows(IndexOutOfBoundsException.class, () -> list.delete(2), "Index equal to size should throw");
        assertThrows(IndexOutOfBoundsException.class, () -> list.delete(100), "Large index should throw");
    }

    @Test
    @DisplayName("delete() on single-element list makes list empty")
    void testDeleteOnlyElement() {
        LinkedList list = new LinkedList();
        list.add(99);
        list.delete(0);
        assertEquals(0, list.size(), "List should be empty after deleting only element");
        assertThrows(IndexOutOfBoundsException.class, () -> list.get(0), "Getting from empty list should throw");
    }
}


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: Implementing size and delete Methods in LinkedList

解答