Testing

As far as commands go, cargo supports test and bench to run a crate's tests. These tests are specified in the code by creating a "module" inside a module and annotating it with #[cfg(test)]. Furthermore, each test also has to be annotated with either #[test] or #[bench], whereas the latter takes an argument to the Bencher, a benchmark runner class that allows us to collect stats on each run:

#![feature(test)] 
extern crate test;

pub fn my_add(a: i32, b: i32) -> i32 {
    a + b
}

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

    #[test] 
    fn this_works() { 
        assert_eq!(my_add(1, 1), 2);
    }
    
    #[test]
    #[should_panic(expected = "attempt to add with overflow")]
    fn this_does_not_work() {
        assert_eq!(my_add(std::i32::MAX, std::i32::MAX), 0);
    }
    
    #[bench]
    fn how_fast(b: &mut Bencher) {
        b.iter(|| my_add(42, 42))
    }
}

After running cargo test, the output is as expected:

Finished dev [unoptimized...