smarm/tests/supervisor.rs

//! One-for-one supervisor tests.
//!
//! A `OneForOne` runs as an ordinary actor: it spawns its children under
//! itself, collects their termination `Signal`s on a single mailbox, and
//! restarts them per policy until either every child is in a terminal,
//! non-restartable state (then `run()` returns) or the restart intensity cap
//! is tripped (then `run()` gives up and returns).
//!
//! Policies:
//!   - `Permanent`  — restart on any termination (normal or panic).
//!   - `Transient`  — restart only on panic; a normal exit is "done".
//!   - `Temporary`  — never restart.
//!
//! All cases below are deterministic under the single-thread runtime: the
//! supervisor parks in `recv()` while a child runs to completion, so signals
//! arrive one at a time in a fixed order.

use smarm::supervisor::{ChildSpec, OneForOne, Restart};
use smarm::{run, spawn};
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::Arc;
use std::time::Duration;

fn counting_child(
    counter: &Arc<AtomicUsize>,
    behavior: impl Fn(usize) + Send + Sync + 'static,
) -> impl Fn() + Send + Sync + 'static {
    let c = counter.clone();
    move || {
        let n = c.fetch_add(1, Ordering::SeqCst) + 1;
        behavior(n);
    }
}

#[test]
fn transient_child_is_restarted_on_panic_then_settles() {
    let runs = Arc::new(AtomicUsize::new(0));
    let r = runs.clone();
    run(move || {
        let child = counting_child(&r, |n| {
            if n < 3 {
                panic!("crash {n}");
            }
            // 3rd run returns normally -> Transient does not restart.
        });
        let sup = spawn(move || {
            OneForOne::new()
                .intensity(10, Duration::from_secs(60))
                .child(ChildSpec::new(Restart::Transient, child))
                .run();
        });
        sup.join().unwrap();
    });
    assert_eq!(runs.load(Ordering::SeqCst), 3, "two restarts then a clean exit");
}

#[test]
fn transient_child_normal_exit_is_not_restarted() {
    let runs = Arc::new(AtomicUsize::new(0));
    let r = runs.clone();
    run(move || {
        let child = counting_child(&r, |_| { /* return normally */ });
        let sup = spawn(move || {
            OneForOne::new()
                .child(ChildSpec::new(Restart::Transient, child))
                .run();
        });
        sup.join().unwrap();
    });
    assert_eq!(runs.load(Ordering::SeqCst), 1);
}

#[test]
fn temporary_child_is_not_restarted_on_panic() {
    let runs = Arc::new(AtomicUsize::new(0));
    let r = runs.clone();
    run(move || {
        let child = counting_child(&r, |_| panic!("once"));
        let sup = spawn(move || {
            OneForOne::new()
                .child(ChildSpec::new(Restart::Temporary, child))
                .run();
        });
        sup.join().unwrap();
    });
    assert_eq!(runs.load(Ordering::SeqCst), 1);
}

#[test]
fn intensity_cap_stops_a_permanent_crash_loop() {
    let runs = Arc::new(AtomicUsize::new(0));
    let r = runs.clone();
    run(move || {
        let child = counting_child(&r, |n| panic!("always {n}"));
        let sup = spawn(move || {
            OneForOne::new()
                .intensity(3, Duration::from_secs(60))
                .child(ChildSpec::new(Restart::Permanent, child))
                .run();
        });
        sup.join().unwrap();
    });
    // 1 initial run + 3 restarts, then the 4th failure trips the cap.
    assert_eq!(runs.load(Ordering::SeqCst), 4);
}

#[test]
fn one_for_one_restarts_only_the_failed_child() {
    let a = Arc::new(AtomicUsize::new(0));
    let b = Arc::new(AtomicUsize::new(0));
    let (ra, rb) = (a.clone(), b.clone());
    run(move || {
        let child_a = counting_child(&ra, |n| {
            if n < 2 {
                panic!("a crash {n}");
            }
        });
        let child_b = counting_child(&rb, |_| { /* runs once, normal */ });
        let sup = spawn(move || {
            OneForOne::new()
                .intensity(10, Duration::from_secs(60))
                .child(ChildSpec::new(Restart::Transient, child_a))
                .child(ChildSpec::new(Restart::Temporary, child_b))
                .run();
        });
        sup.join().unwrap();
    });
    assert_eq!(a.load(Ordering::SeqCst), 2, "A restarts once then settles");
    assert_eq!(b.load(Ordering::SeqCst), 1, "B is untouched by A's restart");
}