Missing number in arithmetic progression

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::missing_number(vec![5, 7, 11, 13]);
    let expected = 9;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::missing_number(vec![15, 13, 12]);
    let expected = 14;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::missing_number(vec![1, 2, 3, 4, 6]);
    let expected = 5;
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::missing_number(vec![0, 0, 0]);
    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::missing_number(vec![10, 20, 40]);
    let expected = 30;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}