解决@Autowired注入失效出现java.lang.NullPointerException

这是我的UserServiceTestCase类：（写法上没什么问题，但是报了一个错）

package com.itheima.service;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.itheima.domain.User;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
public class UserServiceTestCase {
    @Autowired
    private UserService userService;
    @Test
   public void testGetById(){
        System.out.println(userService.getById(1));
    }
    @Test
    public void testSave() {
        User user=new User();
        user.setUserid(1);
        user.setUsername("Test1");
        user.setPassword("123456");
        System.out.println(userService.save(user) );
    }
    @Test
    public void testUpdate() {
        User user=new User();
        user.setUserid(2);
        user.setUsername("test2");
        user.setPassword("123456");
        System.out.println( userService.update(user));
    }
    @Test
    public void testDelete() {
        System.out.println( userService.delete(12));
    }
    @Test
    public void testGetALL() {
        System.out.println( userService.getAll());
    }
    @Test
    public  void testPage() {
        IPage page = userService.getPage(1,3);
        System.out.println(page.getCurrent());
        System.out.println(page.getPages());
        System.out.println(page.getSize());
        System.out.println(page.getRecords());
        System.out.println(page.getTotal());
    }
}

 这是错误信息：

修改后：