cargo-mutants 27.0.0

Inject bugs and see if your tests catch them
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//! An example of a function that will hang when mutated.
//!
//! An attribute could be added to avoid mutating it, but this tree
//! lets us test the case where that has not yet been fixed.

use std::sync::atomic::{AtomicBool, Ordering};
use std::time::{Duration, Instant};

static TRIGGER: AtomicBool = AtomicBool::new(false);

/// Normally, this will return false the first time it is called, and then true.
///
/// If mutated to just return false, the program will spin forever.
fn should_stop() -> bool {
    if TRIGGER.load(Ordering::Relaxed) {
        return true;
    }
    TRIGGER.store(true, Ordering::Relaxed);
    false
}

/// Runs until `should_stop` returns true, and then returns the number
/// of iterations.
///
/// Also stops after a few minutes anyhow, so that if the timeouts are not
/// properly implemented, the child process doesn't hang around forever.
pub fn controlled_loop() -> usize {
    let start = Instant::now();
    for i in 1.. {
        println!("{}", i);
        if should_stop() {
            return i;
        }
        std::thread::sleep(std::time::Duration::from_millis(100));
        if start.elapsed() > Duration::from_secs(60) {
            panic!("timed out");
        }
    }
    unreachable!();
}

mod test {
    #[test]
    fn controlled_loop_terminates() {
        // Should do two passes: first the trigger is false but gets set,
        // then the trigger is true and the loop terminates.
        assert_eq!(super::controlled_loop(), 2);
    }
}