package com.example;

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

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.util.regex.Pattern;

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

public class MainTest {
    @Test
    @DisplayName("printWelcome prints correct welcome message")
    void testPrintWelcome() {
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));

        Main.printWelcome();

        System.setOut(originalOut);
        String output = outContent.toString().trim();
        Pattern pattern = Pattern.compile(
            "welcome\\\\s+to\\\\s+the\\\\s+java\\\\s+methods\\\\s+challenge!",
            Pattern.CASE_INSENSITIVE
        );
        assertTrue(pattern.matcher(output).find(), "Expected welcome message, got: '" + output + "'");
    }

    @Test
    @DisplayName("showInstructions prints correct instruction message")
    void testShowInstructions() {
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));

        Main.showInstructions();

        System.setOut(originalOut);
        String output = outContent.toString().trim();
        Pattern pattern = Pattern.compile(
            "follow\\\\s+the\\\\s+instructions\\\\s+carefully\\\\s+to\\\\s+complete\\\\s+the\\\\s+task\\\\s*\\\\.",
            Pattern.CASE_INSENSITIVE
        );
        assertTrue(pattern.matcher(output).find(), "Expected instructions message, got: '" + output + "'");
    }

    @Test
    @DisplayName("printCompletion prints correct completion message")
    void testPrintCompletion() {
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));

        Main.printCompletion();

        System.setOut(originalOut);
        String output = outContent.toString().trim();
        Pattern pattern = Pattern.compile(
            "congratulations!\\\\s+you\\\\s+have\\\\s+completed\\\\s+the\\\\s+challenge\\\\s*\\\\.",
            Pattern.CASE_INSENSITIVE
        );
        assertTrue(pattern.matcher(output).find(), "Expected completion message, got: '" + output + "'");
    }

    @Test
    @DisplayName("main prints all messages in order")
    void testMainAllMessages() {
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        PrintStream originalOut = System.out;
        System.setOut(new PrintStream(outContent));

        Main.main(new String[]{});

        System.setOut(originalOut);
        String output = outContent.toString().toLowerCase();
        int idxWelcome = output.indexOf("welcome to the java methods challenge!");
        int idxInstructions = output.indexOf("follow the instructions carefully to complete the task.");
        int idxCompletion = output.indexOf("congratulations! you have completed the challenge.");
        assertTrue(idxWelcome != -1, "Welcome message missing");
        assertTrue(idxInstructions != -1, "Instructions message missing");
        assertTrue(idxCompletion != -1, "Completion message missing");
        assertTrue(idxWelcome < idxInstructions && idxInstructions < idxCompletion,
            "Messages are not printed in the correct order");
    }
}

MainTest.java

A hands-on introduction to Java methods, data transfer, and compiler behavior. Learn how to declare, invoke, and overload methods, work with parameters and arguments, understand pass-by-value, and implement recursion for problem-solving.

Challenge: Basic Method Creation

解答