Why is Springboot's JPA entity abstract?

Question

I inherited a Springboot based piece of software, in which each entity is represented by at least two data types. For example:

The DTO:

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class MyEntityDTO {
    Long id;
    String name;
    String description;
    String type;
    Long parentId;
    String parentSerialNumber;
}

The corresponding JPA entity (table):

@DiscriminatorColumn(name = "type")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@Table(name = "my_entities_table")
@Entity

@NoArgsConstructor
@Data
@SuperBuilder
@FieldDefaults(level = AccessLevel.PRIVATE)
public abstract class MyEntity extends IdBasedEntity {
    @ManyToOne(fetch = FetchType.EAGER)
    @JsonIgnore
    Parent parent;
    @Column(name = "type", insertable = false, updatable = false, nullable = false)
    String type;
    @Column(nullable = false)
    String externalId;

    @Column(nullable = false)
    String myentityName;
    @Column
    String description;
}

My question is: What design principles and/or patterns does an abstract JPA entity satisfy?

I am trying to understand this because I was surprised to discover that I cannot mock this entity in a JUnit. I am assuming there is a good design reason for this.

Answer 1

To complete @Chris comment.

According to JPA specification

An entity may inherit from a superclass that provides persistent entity state and mapping information, but which is not itself an entity. Typically, the purpose of such a mapped superclass is to define state and mapping information that is common to multiple entity classes.