报错内容：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'com.pblog.PblogApplicationTests': Unsatisfied dependency expressed through field 'userMapper'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.pblog.dao.UserMapper' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.pblog.dao.UserMapper' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

单元测试文件内容：

package com.pblog;

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;

import com.pblog.dao.UserMapper;
import com.pblog.domain.User;

@RunWith(SpringRunner.class)
@SpringBootTest
public class PblogApplicationTests {
    
        @Autowired
        private UserMapper userMapper;
        @Test
        public void userDaoTest() {
            User user=new User();
            user.setUserName("刘备");
            user.setUserEmail("1111111111@qq.com");
            user.setUserPwd("123456");
            int n=userMapper.insert(user);
            if(n>0) {
                System.out.println("插入成功");
            }else {
                System.out.println("插入失败");
            }
        }
    
}

出错原因：spring找不到bean(UserMapper)

找到项目启动文件Application.java，内容如下：

package com.pblog;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class PblogApplication {

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

解决办法：在项目的启动类中加入MapperScan注解。

修改后的Application.java文件如下：

package com.pblog;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.pblog.dao")
public class PblogApplication {

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

重新启动项目成功。