Benchmark with tarai function for Rust

benchmark.rs

#![feature(test)]

extern crate test;

pub fn tarai(x: i32, y: i32, z: i32) -> i32 {
    if x <= y {
        y
    } else {
        tarai(tarai(x-1, y, z), tarai(y-1, z, x), tarai(z-1, x, y))
    }
}

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

    #[test]
    fn it_works() {
        assert_eq!(10, tarai(4, 10, 2));
    }

    #[bench]
    fn bench_tarai(b: &mut Bencher) {
        b.iter(|| {
            let x = test::black_box(13);
            let y = test::black_box(5);
            let z = test::black_box(0);
            tarai(x, y, z)
        });
    }
}