问Junit测试单独通过，但在一起运行时会失败

EN

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

import java.text.ParseException;

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

import main.Appointment;
import main.AppointmentService;

class AppointmentServiceTest {

    private static AppointmentService appointmentService;
    
    @BeforeAll
    static void setUp() {
        appointmentService = AppointmentService.getService();
    }
    
    @Test
    void testAddAppointmentSuccess() throws ParseException {
        Appointment appointment = new Appointment("123456", "2022-10-01", "Appointment Description String");
        assertTrue(appointmentService.addAppointment(appointment));
        
        Appointment cachedAppointment = appointmentService.getAppointment(appointment.getAppointmentId());
        
        assertTrue(cachedAppointment != null);
        assertTrue(cachedAppointment.getAppointmentId().equals("123456"));
        assertTrue(cachedAppointment.getAppointmentDate().equals("2022-10-01"));
        assertTrue(cachedAppointment.getAppointmentDescription().equals("Appointment Description String")); 
    }
    
    @Test
    void testAddMultipleAppointmentsSuccess() throws ParseException {
        Appointment appointment1 = new Appointment("123456", "2022-10-01", "Appointment Description String");
        Appointment appointment2 = new Appointment("1234567", "2022-10-02", "Appointment Description String2");
        
        assertTrue(appointmentService.addAppointment(appointment1));
        Appointment cachedAppointment1 = appointmentService.getAppointment(appointment1.getAppointmentId());
        
        assertTrue(cachedAppointment1 != null);
        assertTrue(cachedAppointment1.getAppointmentId().equals("123456"));
        assertTrue(cachedAppointment1.getAppointmentDate().equals("2022-10-01"));
        assertTrue(cachedAppointment1.getAppointmentDescription().equals("Appointment Description String"));    
        
        assertTrue(appointmentService.addAppointment(appointment2));
        Appointment cachedAppointment2 = appointmentService.getAppointment(appointment1.getAppointmentId());
        
        assertTrue(cachedAppointment2 != null);
        assertTrue(cachedAppointment2.getAppointmentId().equals("1234567"));
        assertTrue(cachedAppointment2.getAppointmentDate().equals("2022-10-02"));
        assertTrue(cachedAppointment2.getAppointmentDescription().equals("Appointment Description String2"));
        
    }
    
    @Test
    void testAddAppoitnmentDuplicateIdFail() throws ParseException {
        Appointment appointment1 = new Appointment("123456", "2022-10-01", "Appointment Description String");
        Appointment appointment2 = new Appointment("123456", "2022-10-01", "Appointment Description String");


        assertTrue(appointmentService.addAppointment(appointment1));
        assertFalse(appointmentService.addAppointment(appointment2));
    }
    
    @Test
    void testGetAppointmentAndUpdateSuccess() throws ParseException {
        Appointment appointment = new Appointment("123456", "2022-10-01", "Appointment Description String");
        assertTrue(appointmentService.addAppointment(appointment));
        
        Appointment updatedAppointment = appointmentService.getAppointment(appointment.getAppointmentId());
        updatedAppointment.setAppointmentDate("2022-10-02");
        updatedAppointment.setAppointmentDescription("New Description");
        
        updatedAppointment = appointmentService.getAppointment(updatedAppointment.getAppointmentId());
        
        assertTrue(updatedAppointment.getAppointmentDescription().equals("New Description"));
        assertTrue(updatedAppointment.getAppointmentDate().equals("2022-10-02"));
    }
    
    @Test
    void testGetAppointmentAndDeleteSuccess() throws ParseException {
        Appointment appointment = new Appointment("123456", "2022-10-01", "Appointment Description String");
        
        assertTrue(appointmentService.addAppointment(appointment));
        
        appointment = appointmentService.getAppointment(appointment.getAppointmentId());
        assertTrue(appointment != null);
        
        assertTrue(appointmentService.deleteAppointment(appointment.getAppointmentId()));
        assertTrue(appointmentService.getAppointment(appointment.getAppointmentId()) == null);
    }
    
    @Test
    void testDeleteInvalidAppointmentFail() {
        String invalidAppointmentIdString = "123";
        
        assertFalse(appointmentService.deleteAppointment(invalidAppointmentIdString));
    }

import java.util.HashMap;
import java.util.Map;

public class AppointmentService {

    private static AppointmentService reference = new AppointmentService();
    private final Map<String, Appointment> appointmentList;
    
    AppointmentService() {
        this.appointmentList = new HashMap<String, Appointment>();
    }
    
    public static AppointmentService getService() {
        return reference;
    }
    
    public boolean addAppointment(Appointment appointment) {
        boolean isSuccess = false;
        
        if(!appointmentList.containsKey(appointment.getAppointmentId())) {
            appointmentList.put(appointment.getAppointmentId(), appointment);
            isSuccess = true;
        }
        return isSuccess;
    }
    
    public boolean deleteAppointment(String appointmentId) {
        return appointmentList.remove(appointmentId) != null;
    }
    
    public Appointment getAppointment(String appointmentId) {
        return appointmentList.get(appointmentId);
    }
    
}