Java输出50道100以内加减法，并编写测试代码

以下是Java输出50道100以内加减法的代码：

import java.util.Random;

public class MathQuiz {
    public static void main(String[] args) {
        Random random = new Random();
        int num1, num2;
        char operator;
        int correctCount = 0;
        int wrongCount = 0;

        for (int i = 1; i <= 50; i++) {
            num1 = random.nextInt(100);
            num2 = random.nextInt(100);
            operator = random.nextInt(2) == 0 ? '+' : '-';
            int answer = 0;

            if (operator == '+') {
                answer = num1 + num2;
            } else {
                answer = num1 - num2;
            }

            System.out.print(i + ". " + num1 + " " + operator + " " + num2 + " = ");

            // 用户输入答案
            int userAnswer = new java.util.Scanner(System.in).nextInt();

            // 判断用户答案是否正确
            if (userAnswer == answer) {
                System.out.println("回答正确！");
                correctCount++;
            } else {
                System.out.println("回答错误！");
                wrongCount++;
            }
        }

        System.out.println("答题结束！共回答了 " + (correctCount + wrongCount) + " 题，其中回答正确 " + correctCount + " 题，回答错误 " + wrongCount + " 题。");
    }
}

以下是测试代码，可以在命令行中运行：

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;

import static org.junit.Assert.assertEquals;

public class MathQuizTest {

    @org.junit.Test
    public void testMain() {
        ByteArrayOutputStream outContent = new ByteArrayOutputStream();
        System.setOut(new PrintStream(outContent));

        String expectedOutput = "";
        int correctCount = 0;
        int wrongCount = 0;

        // 模拟用户输入
        String input = "";
        for (int i = 1; i <= 50; i++) {
            int num1 = (int) (Math.random() * 100);
            int num2 = (int) (Math.random() * 100);
            char operator = Math.random() > 0.5 ? '+' : '-';
            int answer = operator == '+' ? num1 + num2 : num1 - num2;
            int userAnswer = (int) (Math.random() * 200);

            input += userAnswer + System.lineSeparator();

            expectedOutput += i + ". " + num1 + " " + operator + " " + num2 + " = ";
            if (userAnswer == answer) {
                expectedOutput += "回答正确！" + System.lineSeparator();
                correctCount++;
            } else {
                expectedOutput += "回答错误！" + System.lineSeparator();
                wrongCount++;
            }
        }

        // 运行程序
        System.setIn(new java.io.ByteArrayInputStream(input.getBytes()));
        MathQuiz.main(new String[]{});

        // 对比输出结果
        String actualOutput = outContent.toString();
        assertEquals(expectedOutput, actualOutput);

        // 对比回答正确和回答错误的数量
        int actualCorrectCount = actualOutput.split("回答正确！").length - 1;
        assertEquals(correctCount, actualCorrectCount);

        int actualWrongCount = actualOutput.split("回答错误！").length - 1;
        assertEquals(wrongCount, actualWrongCount);
    }
}