MemberService

pakage hello.core.member;
public enum Grade {
    BASIC,
    VIP
}
// Grade.java

pakage hello.core.member;

public class Member {

    private Long id;
    private String name;
    private  Grade grade;

    public Member(Long id, String name, Grade grade) {
        this.id = id;
        this.name = name;
        this.grade = grade;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Grade getGrade() {
        return grade;
    }

    public void setGrade(Grade grade) {
        this.grade = grade;
    }
}
//Member.java

package hello.core.member;

public interface MemberService {

    void join(Member member);

    Member findMember(Long memberId);
}
// MemberService.java

package hello.core.member;

public interface MemberRepository {

    void save(Member member);

    Member findById(Long memberId);
}
// MemberRepository.java

package hello.core.member;

import java.util.HashMap;
import java.util.Map;

public class MemoryMemberRepository implements MemberRepository{

    private static Map<Long, Member> store = new HashMap<>();

    @Override
    public void save(Member member) {
        store.put(member.getId(), member);
    }

    @Override
    public Member findById(Long memberId) {
        return store.get(memberId);
    }
}
// MemoryMemberRepository.java

package hello.core.member;

public class MemberServiceImpl implements MemberService {

    private final MemberRepository memberRepository = new MemoryMemberRepository();

    @Override
    public void join(Member member) {
        memberRepository.save(member);
    }

    @Override
    public Member findMember(Long memberId) {
        return memberRepository.findById(memberId);
    }
}
// MemberServiceImpl.java

package hello.core.member;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;

public class MemberServiceTest {

    MemberService memberService = new MemberServiceImpl();

    @Test
    void join(){
        //given ~가 주어졌을 때
        Member member = new Member(1L, "memberA", Grade.VIP);

        //when ~이렇게 실행했을 때
        memberService.join(member);
        Member findMember = memberService.findMember(1L);

        //then 결과가 이렇다.
        Assertions.assertThat(member).isEqualTo(findMember);
    }
}
// MemberServiceTest.java