public boolean isAdmin() {
        return this.memberRole.isAdministrator();
    }
@Test
    void 어드민인_경우에_true를_반환한다() {
        // given
        Member admin = 어드민_유저_생성();

        // when
        boolean result = admin.isAdmin();

        // then
        assertThat(result).isTrue();
    }