为什么测试“test_inputstream......”成功了，难道不应该是失败吗？

问：

package com.skilldistillery.lordo.app;

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

import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;

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

class UITest {

    Scanner sc = new Scanner(System.in);
    InputStream mockInputStream;
    
    @BeforeEach
    void init() {
        // This will run once before any of the test methods in the class.
        mockInputStream = new MockInputStream();
        System.setIn(mockInputStream);
    }

    @Test
    void test_inputstream_fails_on_mismatch() {
        assertEquals("quiffdt", sc.nextLine());
    }

}
class MockGame implements CLIGame {
    @Override
    public void pushEvent(GameEvent event) {}
}

class MockInputStream extends InputStream {

    private byte[] inputBytes;
    private int position = 0;

    public MockInputStream() {
        String input = "quit" + System.lineSeparator();
        this.inputBytes = input.getBytes();
    }

    @Override
    public int read() throws IOException {
        if (position < inputBytes.length) {
            return inputBytes[position++];
        } else {
            return -1;
        }
    }
    
    @Override
    public void close() throws IOException {
        super.close();
    }
}

我真的是 java 的新手，但我认为通过将我的输入流设置为自定义流，我可以模拟输入流。这是不正确的吗？我试图为我正在从事的项目设置一个模拟。我可能完全错了，我只是不确定。