pub fn is_palindrome(number: i32) -> bool {
  // Negative numbers can never be a palindrome because of the minus sign.
  if number < 0 {
    return false;
  }

  let number_string = number.to_string();
  number_string == number_string.chars().rev().collect::<String>()
}

#[test]
fn test_palindrome_number() {
  assert!(is_palindrome(0));
  assert!(is_palindrome(-0));
  assert!(is_palindrome(1));
  assert!(is_palindrome(121));
  assert!(is_palindrome(12321));

  assert!(!is_palindrome(123));
  assert!(!is_palindrome(321));
  assert!(!is_palindrome(10));
  assert!(!is_palindrome(-121));
}