我正在尝试使用Junit编写测试方法：我可以一起使用assertNull和assertNotNull语句吗？

如何解决我正在尝试使用Junit编写测试方法：我可以一起使用assertNull和assertNotNull语句吗？

 'I'm trying to write a test method with Junit: Can I use assertNull and assertNotNull statements together?  I may have used it incorrectly because I am trying to learn.

我可能也误解了单元测试逻辑。你能帮我吗？'

   ' My codes:'
     public static TtVaeTarifeTipi getMaxDownloadVeUploadaSahipTtVaeTarifeTipi(List<TtVaeTarifeTipi> ttVaeTarifeTipiListe) {
            if (ttVaeTarifeTipiListe.isEmpty() || ttVaeTarifeTipiListe == null) {
                return null;
            }
            else{
                Map<Integer,List<TtVaeTarifeTipi>> downloadaGoreGruplanmisTtVaeTarifeTipleriMap = ttVaeTarifeTipiListe.stream().collect(groupingBy(t -> t.getTtVaePaket().getDownload()));
                Integer maxHizDegeri = downloadaGoreGruplanmisTtVaeTarifeTipleriMap.entrySet().stream().max(Map.Entry.comparingByKey()).get().getKey();
                List<TtVaeTarifeTipi> maxDownloadaSahipTtVaeTarifeTipleri = downloadaGoreGruplanmisTtVaeTarifeTipleriMap.get(maxHizDegeri);
                return maxDownloadaSahipTtVaeTarifeTipleri.stream().max(Comparator.comparing(t -> t.getTtVaePaket().getUpload())).get();
    
            }
        }
   'and test codes:
      @Test
        @Transactional
        public void testMaxDownloadVeUploadaSahipTtVaeTarifeTipi() {
            List<TtVaeTarifeTipi> ttVaeTarifeTipiListe = getornekTtVaeTarifeTiplieri();
            if (ttVaeTarifeTipiListe.isEmpty() || ttVaeTarifeTipiListe == null) {
                Assert.assertNull(TtVaeUtils.getMaxDownloadVeUploadaSahipTtVaeTarifeTipi(ttVaeTarifeTipiListe));
            } else {
                Assert.assertNotNull(TtVaeUtils.getMaxDownloadVeUploadaSahipTtVaeTarifeTipi(ttVaeTarifeTipiListe));
            }
        }

我可以一起使用assertNull和assertNotNull语句吗？我可能没有正确使用它，因为我正在尝试学习。