[Jpa][test] JPA EntityManager 연습하기

@Transactional
@SpringBootTest
@Rollback(value = false)
class MemberTest {

    @PersistenceContext
    EntityManager em;
    @Test
    public void testEntity() {
        Team teamA = new Team("teamA");
        Team teamB = new Team("teamB");
        em.persist(teamA);
        em.persist(teamB);

        Member member1 = new Member("member1", 10, teamA);
        Member member2 = new Member("member2", 20, teamA);
        Member member3 = new Member("member3", 30, teamB);
        Member member4 = new Member("member4", 40, teamB);

        em.persist(member1);
        em.persist(member2);
        em.persist(member3);
        em.persist(member4);
        //초기화
        em.flush();
        em.clear();
        //확인
        List<Member> members = em.createQuery("select m from Member m", Member.class).getResultList();
        for (Member member : members) {
            System.out.println("member = " + member);
            System.out.println("-> member.Team = " + member.getTeam());
        }
    }
}

test에서 EntityManager를 꺼내서 

em.createQuery등을 활용해서 join fetch등의 옵션활용해서 성능 최적화를 한 후 ㅇ넣어보자!