@Test
  public void testCountStringWithNull() throws HiveException {
    testAggregateString(
        "count",
        2,
        Arrays.asList(new Object[]{"A",null,"C", "D", null}),
        3L);
  }
Unit test for the vectorized GROUP BY operator.
ql/src/test/org/apache/hadoop/hive/ql/exec/vector/TestVectorGroupByOperator.java