Number of digit one

#[test]
fn test_example_1() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(13);
    let expected = 6;
    log_result!(val == expected, "test_example_1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_example_2() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(0);
    let expected = 0;
    log_result!(val == expected, "test_example_2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_larger_number() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(1000);
    let expected = 301;
    log_result!(val == expected, "test_larger_number", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_round_number() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(100);
    let expected = 21;
    log_result!(val == expected, "test_round_number", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_single_digit_with_1() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(1);
    let expected = 1;
    log_result!(val == expected, "test_single_digit_with_1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_single_digit_without_1() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(5);
    let expected = 1;
    log_result!(val == expected, "test_single_digit_without_1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn test_two_digits() {
    let start = std::time::Instant::now();
    let val = Solution::count_digit_one(20);
    let expected = 12;
    log_result!(val == expected, "test_two_digits", start, &expected, &val);
    assert_eq!(val, expected);
}