Java Spring Boot应用中的单元测试与集成测试：以数据库交互为例

<!-- Spring Boot Web Starter (for Controller) -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- Spring Boot Data JPA Starter (for Repository and Entity) -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- MySQL Driver -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
</dependency>
<!-- Lombok (for @Data, @Builder etc.) -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

<!-- Spring Boot Test Starter (includes JUnit 5, Mockito, Spring Test) -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>
<!-- Testcontainers for MySQL (for Integration Tests) -->
<dependency>
    <groupId>org.testcontainers</groupId>
    <artifactId>mysql</artifactId>
    <scope>test</scope>
</dependency>
<!-- Testcontainers JUnit Jupiter integration -->
<dependency>
    <groupId>org.testcontainers</groupId>
    <artifactId>junit-jupiter</artifactId>
    <scope>test</scope>
</dependency>

// 实体类：Message.java
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.persistence.*; // 注意：如果使用Spring Boot 3+，请使用jakarta.persistence

@Entity
@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Message {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String name;
    private String mail;
    private String message;
}

// DTO类：MessageDto.java
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class MessageDto {
    private Long id;
    private String title;
    private String name;
    private String mail;
    private String message;
}

// JPA Repository 接口：MessageRepository.java
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface MessageRepository extends JpaRepository<Message, Long> {
}

// Service 层：MessageService.java
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Service;

@Service
@RequiredArgsConstructor
public class MessageService {

    private final MessageRepository messageRepository;

    public Message saveMessage(Message message) {