message: Add multi column GROUP BY test case to tests/aggregate.rs,
  SELECT .... GROUP BY id, city
diff: @@ -144,6 +144,10 @@ pub fn group_by(mut tester: impl tests::Tester) {
  5 "Seattle".to_owned()
  ),
  ),
  + (
  + "SELECT ratio FROM Item GROUP BY id, city",
  + select!(F64; 0.2; 0.9; 1.1; 3.2; 11.1; 6.11),
  + ),
  ];
  test_cases
  