Power of four

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

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

#[test]
fn test_power_of_four() {
    let start = std::time::Instant::now();
    let val = Solution::is_power_of_four(16);
    let expected = true;
    log_result!(val == expected, "test_power_of_four", start, &expected, &val);
    assert_eq!(val, expected);
}