@Test
  public void testGetOldestTombstoneForReplicateTombstoneSweeper() {
    VM server1 = VM.getVM(0);
    VM server2 = VM.getVM(1);

    server1.invoke(() -> {
      createCacheAndRegion(REPLICATE);
      region.put("K1", "V1");
      region.put("K2", "V2");
    });

    server2.invoke(() -> createCacheAndRegion(REPLICATE));

    server1.invoke(() -> {
      // Send tombstone gc message to vm1.
      region.destroy("K1");

      TombstoneService.TombstoneSweeper tombstoneSweeper =
          ((InternalCache) cache).getTombstoneService().getSweeper((LocalRegion) region);

      assertThat(tombstoneSweeper.getOldestTombstone()).contains("K1");
      performGC(1);
      assertThat(tombstoneSweeper.getOldestTombstone()).isNull();
    });
  }
The purpose of this test is for a replicate region scenario to get the oldest tombstone
and validate that it matches the tombstone of the entry we removed.
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/versions/TombstoneDUnitTest.java