@Test
public void testGroupByClause() {

  Parser<GroupBy> parser = RelationParser.groupByClause(ExpressionParser.NUMBER, ExpressionParser.NUMBER);
  TerminalParserTest.assertParser(parser, "group by 1, 2", new GroupBy(Arrays.asList(ExpressionParserTest.number(1), ExpressionParserTest.number(2)), null));
  TerminalParserTest.assertParser(parser, "group by 1, 2 having 3",
      new GroupBy(Arrays.asList(ExpressionParserTest.number(1), ExpressionParserTest.number(2)), ExpressionParserTest.number(3)));
}