@Test
public void assertInputGroupIsEmpty() throws SQLException {

    CountDownLatch latch = new CountDownLatch(1);
    List<String> actual = shardingExecuteEngine.groupExecute(new LinkedList<ShardingExecuteGroup<StatementExecuteUnit>>(), new MockGroupExecuteCallback(latch));
    latch.countDown();
    assertThat(actual.size(), is(0));
}