Actual Output different to expected output
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package org.example;

import org.example.cmd.CmdRegister;
import org.example.day.SystemDate;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.lang.reflect.Field;
import java.util.ArrayList;

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

class CmdRegisterTest {

    private CmdRegister cmd;
    private Library library;

    private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
    private final ByteArrayOutputStream errContent = new ByteArrayOutputStream();

    @BeforeEach
    public void resetInstance() throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
        Field systemDateInstance = SystemDate.class.getDeclaredField("instance");
        systemDateInstance.setAccessible(true);
        systemDateInstance.set(null, null);

        Field instance = Library.class.getDeclaredField("instance");
        instance.setAccessible(true);
        instance.set(null, null);

        SystemDate.createTheInstance("01-Jan-2020");
        library = Library.getInstance();

        Field field = library.getClass().getDeclaredField("allMembers");
        field.setAccessible(true);
        ArrayList<Member> allMembers = (ArrayList<Member>) field.get(library);
        allMembers.clear();

        Field field2 = library.getClass().getDeclaredField("allGears");
        field2.setAccessible(true);
        ArrayList<Member> allGears = (ArrayList<Member>) field2.get(library);
        allGears.clear();

        System.setOut(new PrintStream(outContent));
        System.setErr(new PrintStream(errContent));
    }

    @Test
    public void testExecuteExMemberIDInUse() {
        Member m = new Member("001", "John");

        cmd.execute(new String[] {"register", m.getId(), m.getName()});
        String expected =
                """
                Member ID already in use: 001 John
                """;
        assertEquals(expected, outContent.toString());
    }