public void add(String element) {
    addAsync(element).toCompletableFuture().join();
  }
@Test
  public void testAdd() throws Exception {
    final FaultTolerantRedisCluster redisCluster = REDIS_CLUSTER_EXTENSION.getRedisCluster();
    final CardinalityEstimator estimator = new CardinalityEstimator(redisCluster, "test", Duration.ofSeconds(1));

    estimator.add("1");

    long count = redisCluster.withCluster(conn -> conn.sync().pfcount("cardinality_estimator::test"));
    assertThat(count).isEqualTo(1).isEqualTo(estimator.estimate());

    estimator.add("2");
    count = redisCluster.withCluster(conn -> conn.sync().pfcount("cardinality_estimator::test"));
    assertThat(count).isEqualTo(2).isEqualTo(estimator.estimate());

    estimator.add("1");
    count = redisCluster.withCluster(conn -> conn.sync().pfcount("cardinality_estimator::test"));
    assertThat(count).isEqualTo(2).isEqualTo(estimator.estimate());
  }