为什么会出现这个问题呢，请大神们帮我解答，求助

public class ShiroTest {
    SimpleAccountRealm simpleAccountRealm =new SimpleAccountRealm();
    @Before
    public void addUser(){
        simpleAccountRealm.addAccount("mark","123456");
    }

    @Test
    public void  testAuthentication(){



        //构建SecurityManager环境
        DefaultSecurityManager defaultSecurityManager =new DefaultSecurityManager();
        defaultSecurityManager.setRealm(simpleAccountRealm);

        //主动提交认证请求
        SecurityUtils.setSecurityManager(defaultSecurityManager);
        Subject subject = SecurityUtils.getSubject();


        UsernamePasswordToken usernamePasswordToken = new UsernamePasswordToken("mark","123456");
        subject.login(usernamePasswordToken);



    }
}