@Test
public void getStaffMembersOfUserReturnsDirectStaffMembersOfUser() {

    // given
    given(hierarchyTreeNodeRepoMock.findByUser(userMock)).willReturn(Optional.of(hierarchyTreeNodeMock));
    given(hierarchyTreeNodeMock.getDirectStaff()).willReturn(List.of(otherHierarchyTreeNodeMock));
    given(otherHierarchyTreeNodeMock.getUser()).willReturn(otherUserMock);
    // when
    var actualStaff = repoUserService.getStaffMembersOfUser(userMock);
    // then
    assertThat(actualStaff).containsExactly(otherUserMock);
}