#[test]
    fn unary_op() {
        let actual = num(5).plus();
        let expected = "+5";
        test_expr(actual, expected);
        
        let actual = num(10).minus();
        let expected = "-10";
        test_expr(actual, expected);

        let actual = (col("count").gt(num(5))).not();
        let expected = "NOT count > 5";
        test_expr(actual, expected);

        let actual = num(10).factorial();
        let expected = "10!";
        test_expr(actual, expected);
    }