public Optional<GroupInformation> findGroupByUuid(DbSession dbSession, String groupUuid) {

    return Optional.ofNullable(dbClient.groupDao().selectByUuid(dbSession, groupUuid))
      .map(group -> groupDtoToGroupInformation(group, dbSession));
  }
@Test
  public void findGroupByUuid_whenGroupDoesntExist_returnsEmptyOptional() {
    when(dbClient.groupDao().selectByUuid(dbSession, GROUP_UUID))
      .thenReturn(null);

    assertThat(groupService.findGroupByUuid(dbSession, GROUP_UUID)).isEmpty();
  }