使用MyBatis-Plus测试报错：xxxMapper，空指针异常：NullPointerException

错误：

java.lang.NullPointerException
    at com.bcl.vacancy.demo.mybatisplus.mytest.MyTest.MyTest(MyTest.java:26)
    at java.util.ArrayList.forEach(ArrayList.java:1259)
    at java.util.ArrayList.forEach(ArrayList.java:1259) 

测试代码：

@SpringBootTest
public class MyTest {

    @Resource
    private UserMapper userMapper;

    @Test
    public void MyTest(){
        User user = new User(11,"三三",201,"女","1");
        int insert = userMapper.insert(user);

        System.out.println("insert = " + insert);
    }
}

解决方法：在测试类头上加入：@SpringBootTest注解，即可解决。