@Override
  public String getGroupKeyString(int rowIndex, int groupKeyColumnIndex) {
    return _groupByResults.get(rowIndex).get("group").get(groupKeyColumnIndex).asText();
  }
@Test
  public void testGetGroupKeyString() {
    // Run the test
    final String result = _groupByResultSetUnderTest.getGroupKeyString(0, 0);

    // Verify the results
    assertEquals("testGroup1", result);
  }