@Test
  public void findMissingKeysTest() throws StoreException {
    List<StoreKey> idsToProvide = new ArrayList<StoreKey>(state.allKeys.keySet());
    Set<StoreKey> nonExistentIds = new HashSet<>();
    for (int i = 0; i < 10; i++) {
      nonExistentIds.add(state.getUniqueId());
    }
    idsToProvide.addAll(nonExistentIds);
    Collections.shuffle(idsToProvide);
    Set<StoreKey> missingKeys = state.index.findMissingKeys(idsToProvide);
    assertEquals("Set of missing keys not as expected", nonExistentIds, missingKeys);
  }
Tests {@link PersistentIndex#findMissingKeys(List)}.
@throws StoreException
ambry-store/src/test/java/com/github/ambry/store/IndexTest.java