@SuppressFBWarnings(
      value = "EI_EXPOSE_REP",
      justification = "groupingExpressions is ImmutableList"
  )
  public List<Expression> getGroupingExpressions() {
    return groupingExpressions;
  }
@Test
  public void shouldMaintainGroupByOrder() {
    // Given:
    final List<Expression> original = ImmutableList.of(exp1, exp2);

    final GroupBy groupBy = new GroupBy(Optional.empty(), original);

    // When:
    final List<Expression> result = groupBy.getGroupingExpressions();

    // Then:
    assertThat(result, is(original));
  }