Count prefixes of a given string

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::count_prefixes(vec!["a".to_string(), "b".to_string(), "c".to_string(), "ab".to_string(), "bc".to_string(), "abc".to_string()], "abc".to_string());
    let expected = 3;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::count_prefixes(vec!["a".to_string(), "a".to_string()], "aa".to_string());
    let expected = 2;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::count_prefixes(vec!["x".to_string(), "y".to_string()], "abc".to_string());
    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::count_prefixes(vec!["abc".to_string()], "abc".to_string());
    let expected = 1;
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::count_prefixes(vec!["ab".to_string(), "abc".to_string(), "abcd".to_string(), "a".to_string()], "abcde".to_string());
    let expected = 4;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}