springboot如何进行简单的测试

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>

@SpringBootApplication
public class Application {
 
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
 
}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)

package com.xxxxxx;
 
import com.xxxx.Application;
import com.xxxxxxm.util.RandomUtil;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
 
@RunWith(SpringRunner.class)
 
@SpringBootTest(classes = Application.class)
public class UtilPay {
    @Autowired
    RandomUtil randomUtil;
    @Test
    public void util(){
        System.out.println(randomUtil.generateUpperString(6));
    }
}