package com.example;

import org.junit.jupiter.api.*;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

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

public class MainTest {

    private UserScores scores;

    @BeforeEach
    void setUp() {
        scores = new UserScores();
        scores.addUser("Alice", 90);
        scores.addUser("Bob", 75);
        scores.addUser("Charlie", 88);
    }

    @Test
    @DisplayName("addUser adds and getUserScore retrieves correct score")
    void testAddAndGetUserScore() {
        assertEquals(90, scores.getUserScore("Alice"), "Alice's score should be 90");
        assertEquals(75, scores.getUserScore("Bob"), "Bob's score should be 75");
        assertEquals(88, scores.getUserScore("Charlie"), "Charlie's score should be 88");
    }

    @Test
    @DisplayName("getUserScore returns null for missing user")
    void testGetUserScoreMissing() {
        assertNull(scores.getUserScore("David"), "Should return null for non-existent user");
    }

    @Test
    @DisplayName("removeUser removes user and getUserScore returns null")
    void testRemoveUser() {
        scores.removeUser("Bob");
        assertNull(scores.getUserScore("Bob"), "After removal, Bob should not be found");
        assertEquals(90, scores.getUserScore("Alice"), "Alice should still be present");
    }

    @Test
    @DisplayName("printAllUsers prints all users and scores, one per line")
    void testPrintAllUsers() {
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));

        scores.printAllUsers();

        System.setOut(originalOut);
        String output = outContent.toString().trim();
        int count = 0;
        if (output.contains("User: Alice, Score: 90")) count++;
        if (output.contains("User: Bob, Score: 75")) count++;
        if (output.contains("User: Charlie, Score: 88")) count++;
        assertEquals(3, count, "Should print all three users");
    }

    @Test
    @DisplayName("printAllUsers prints after removal")
    void testPrintAllUsersAfterRemoval() {
        scores.removeUser("Bob");
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));

        scores.printAllUsers();

        System.setOut(originalOut);
        String output = outContent.toString().trim();
        assertTrue(output.contains("User: Alice, Score: 90"), "Should contain Alice");
        assertFalse(output.contains("User: Bob, Score: 75"), "Should not contain Bob");
        assertTrue(output.contains("User: Charlie, Score: 88"), "Should contain Charlie");
    }
}


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: Store and Retrieve User Scores

解答