Add two integers

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::sum(12, 5);
    let expected = 17;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::sum(-10, 4);
    let expected = -6;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::sum(0, 0);
    let expected = 0;
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::sum(-100, 100);
    let expected = 0;
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::sum(50, 50);
    let expected = 100;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}