Implementing the fibonacci series using Rust's Iterator

fibonacci.rs

// Author: Victor I. Afolabi
// Implementing the Fibonacci series using Rust's Iterator

#[derive(Debug, PartialEq, PartialOrd)]
pub struct Fib {
  current: usize,
  next: usize,
}

impl Fib {
  pub fn new() -> Fib {
    Fib::default()
  }

  pub fn n_fib(n: usize) -> Vec<usize> {
    Fib::default().take(n).collect::<Vec<usize>>()
  }
}

impl Default for Fib {
  fn default() -> Fib {
    Fib {
      current: 1,
      next: 1,
    }
  }
}

impl Iterator for Fib {
  type Item = usize;

  fn next(&mut self) -> Option<Self::Item> {
    let next: Self::Item = self.current + self.next;
    self.current = self.next;
    self.next = next;
    Some(next)
  }
}

#[cfg(test)]
mod test {
  use super::*;

  #[test]
  fn default() {
    let n_fib: Vec<usize> = Fib::default().take(5).collect::<Vec<usize>>();
    assert_eq!(n_fib, [2, 3, 5, 8, 13]);
  }

  #[test]
  fn next() {
    let mut f = Fib::new();

    assert_eq!(f.next(), Some(2));
    assert_eq!(f.next(), Some(3));
    assert_eq!(f.next(), Some(5));
    assert_eq!(f.next(), Some(8));
  }

  #[test]
  fn n_fib() {
    let n_fib = Fib::n_fib(5);
    assert_eq!(n_fib, [2, 3, 5, 8, 13]);
  }
}