From 26547d2aa52c3b3ce70f847815361a0e3f92707c Mon Sep 17 00:00:00 2001
From: Zachery Aaron Shores-Chmielewski <zachanon@gmail.com>
Date: Fri, 6 Feb 2026 19:05:50 +0700
Subject: [PATCH] feat: worker thread api

Make the worker thread api clearly seperated and ready for test harness
---
 Cargo.toml                   |   4 +
 benches/worker_benchmarks.rs | 153 +++++++++
 src/worker.rs                | 630 +++++++++++++++++++++++++++++++++++
 3 files changed, 787 insertions(+)
 create mode 100644 benches/worker_benchmarks.rs

diff --git a/Cargo.toml b/Cargo.toml
index c223be1..353f364 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,3 +25,7 @@ criterion = { version = "0.5", features = ["html_reports"] }
 [[bench]]
 name = "runtime_benchmarks"
 harness = false
+
+[[bench]]
+name = "worker_benchmarks"
+harness = false
diff --git a/benches/worker_benchmarks.rs b/benches/worker_benchmarks.rs
new file mode 100644
index 0000000..7db7129
--- /dev/null
+++ b/benches/worker_benchmarks.rs
@@ -0,0 +1,153 @@
+use criterion::{
+    criterion_group, criterion_main, BenchmarkId, Criterion, Throughput,
+};
+use swactor::worker::Mailbox;
+
+// ---------------------------------------------------------------------------
+// Push throughput
+// ---------------------------------------------------------------------------
+
+fn mailbox_push(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mailbox_push");
+    for n in [100, 1_000, 10_000] {
+        group.throughput(Throughput::Elements(n as u64));
+        group.bench_with_input(BenchmarkId::from_parameter(n), &n, |b, &n| {
+            b.iter(|| {
+                let mut mb: Mailbox<u64> = Mailbox::new(n);
+                for i in 0..n {
+                    mb.push(i as u64);
+                }
+            });
+        });
+    }
+    group.finish();
+}
+
+// ---------------------------------------------------------------------------
+// Pop throughput
+// ---------------------------------------------------------------------------
+
+fn mailbox_pop(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mailbox_pop");
+    for n in [100, 1_000, 10_000] {
+        group.throughput(Throughput::Elements(n as u64));
+        group.bench_with_input(BenchmarkId::from_parameter(n), &n, |b, &n| {
+            b.iter_batched(
+                || {
+                    let mut mb: Mailbox<u64> = Mailbox::new(n);
+                    for i in 0..n {
+                        mb.push(i as u64);
+                    }
+                    mb
+                },
+                |mut mb| {
+                    for _ in 0..n {
+                        std::hint::black_box(mb.pop());
+                    }
+                },
+                criterion::BatchSize::SmallInput,
+            );
+        });
+    }
+    group.finish();
+}
+
+// ---------------------------------------------------------------------------
+// Interleaved push+pop
+// ---------------------------------------------------------------------------
+
+fn mailbox_interleaved(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mailbox_interleaved");
+    for n in [100, 1_000, 10_000] {
+        group.throughput(Throughput::Elements(n as u64 * 2));
+        group.bench_with_input(BenchmarkId::from_parameter(n), &n, |b, &n| {
+            b.iter(|| {
+                let mut mb: Mailbox<u64> = Mailbox::new(n);
+                for i in 0..n {
+                    mb.push(i as u64);
+                    std::hint::black_box(mb.pop());
+                }
+            });
+        });
+    }
+    group.finish();
+}
+
+// ---------------------------------------------------------------------------
+// drain_count O(1) verification
+// ---------------------------------------------------------------------------
+
+fn mailbox_drain_count(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mailbox_drain_count");
+
+    // Below waterlevel
+    group.bench_function("below", |b| {
+        let mut mb: Mailbox<u64> = Mailbox::new(100);
+        for i in 0..50 {
+            mb.push(i);
+        }
+        b.iter(|| std::hint::black_box(mb.drain_count()));
+    });
+
+    // At waterlevel
+    group.bench_function("at", |b| {
+        let mut mb: Mailbox<u64> = Mailbox::new(100);
+        for i in 0..100 {
+            mb.push(i);
+        }
+        b.iter(|| std::hint::black_box(mb.drain_count()));
+    });
+
+    // Above waterlevel
+    group.bench_function("above", |b| {
+        let mut mb: Mailbox<u64> = Mailbox::new(100);
+        for i in 0..500 {
+            mb.push(i);
+        }
+        b.iter(|| std::hint::black_box(mb.drain_count()));
+    });
+
+    group.finish();
+}
+
+// ---------------------------------------------------------------------------
+// Simulated actor tick: drain_count + pop N
+// ---------------------------------------------------------------------------
+
+fn mailbox_actor_tick(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mailbox_actor_tick");
+
+    for (wl, fill) in [(10, 5), (10, 10), (10, 50), (100, 200)] {
+        let param = format!("wl={wl},fill={fill}");
+        group.bench_function(BenchmarkId::from_parameter(&param), |b| {
+            b.iter_batched(
+                || {
+                    let mut mb: Mailbox<u64> = Mailbox::new(wl);
+                    for i in 0..fill {
+                        mb.push(i as u64);
+                    }
+                    mb
+                },
+                |mut mb| {
+                    let n = mb.drain_count();
+                    for _ in 0..n {
+                        std::hint::black_box(mb.pop());
+                    }
+                },
+                criterion::BatchSize::SmallInput,
+            );
+        });
+    }
+
+    group.finish();
+}
+
+criterion_group!(
+    benches,
+    mailbox_push,
+    mailbox_pop,
+    mailbox_interleaved,
+    mailbox_drain_count,
+    mailbox_actor_tick,
+);
+criterion_main!(benches);
diff --git a/src/worker.rs b/src/worker.rs
index 1ca7c0f..ce68336 100644
--- a/src/worker.rs
+++ b/src/worker.rs
@@ -256,3 +256,633 @@ impl<M: Message> Mailbox<M> {
     }
 }
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::any::Any;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::sync::Arc;
+
+    // ── Test helpers ────────────────────────────────────────────────────
+
+    #[derive(Clone, Debug, PartialEq)]
+    struct TestMsg(u64);
+
+    /// A minimal actor that counts how many messages it handled.
+    struct CounterActor {
+        mailbox: Mailbox<u64>,
+        counter: Arc<AtomicUsize>,
+    }
+
+    impl AnyActor for CounterActor {
+        fn tick(&mut self, _inner: &dyn ContextInner) -> bool {
+            let n = self.mailbox.drain_count();
+            if n > 0 {
+                for _ in 0..n {
+                    if self.mailbox.pop().is_some() {
+                        self.counter.fetch_add(1, Ordering::Relaxed);
+                    }
+                }
+            }
+            n > 0
+        }
+
+        fn deliver(&mut self, msg: Box<dyn Any + Send>) -> bool {
+            if let Ok(typed) = msg.downcast::<u64>() {
+                self.mailbox.push(*typed);
+                true
+            } else {
+                false
+            }
+        }
+    }
+
+    fn make_test_actor(
+        _addr: ActorAddress,
+        waterlevel: usize,
+    ) -> (Box<dyn AnyActor>, Arc<AtomicUsize>) {
+        let counter = Arc::new(AtomicUsize::new(0));
+        let actor = CounterActor {
+            mailbox: Mailbox::new(waterlevel),
+            counter: counter.clone(),
+        };
+        (Box::new(actor), counter)
+    }
+
+    /// No-op ContextInner for ActorPool tests.
+    struct StubContextInner {
+        waterlevel: usize,
+    }
+
+    impl ContextInner for StubContextInner {
+        fn send_any(&self, _addr: ActorAddress, _msg: Box<dyn Any + Send>) -> Result<(), Error> {
+            Ok(())
+        }
+
+        fn spawn_any(
+            &self,
+            _addr: ActorAddress,
+            _actor: Box<dyn AnyActor>,
+        ) -> Result<(), Error> {
+            Ok(())
+        }
+
+        fn mailbox_waterlevel(&self) -> usize {
+            self.waterlevel
+        }
+    }
+
+    fn make_addr(id: u8) -> ActorAddress {
+        let mut bytes = [0u8; 32];
+        bytes[0] = id;
+        ActorAddress(bytes)
+    }
+
+    // ── Mailbox tests ───────────────────────────────────────────────────
+
+    #[test]
+    fn mailbox_new_is_empty() {
+        let mb: Mailbox<u64> = Mailbox::new(10);
+        assert_eq!(mb.len(), 0);
+        assert!(mb.is_empty());
+    }
+
+    #[test]
+    fn mailbox_push_increments_len() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        mb.push(1);
+        assert_eq!(mb.len(), 1);
+        mb.push(2);
+        assert_eq!(mb.len(), 2);
+    }
+
+    #[test]
+    fn mailbox_pop_returns_fifo_order() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        mb.push(10);
+        mb.push(20);
+        mb.push(30);
+        assert_eq!(mb.pop(), Some(10));
+        assert_eq!(mb.pop(), Some(20));
+        assert_eq!(mb.pop(), Some(30));
+    }
+
+    #[test]
+    fn mailbox_pop_empty_returns_none() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        assert_eq!(mb.pop(), None);
+    }
+
+    #[test]
+    fn mailbox_pop_drains_to_empty() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        mb.push(1);
+        mb.push(2);
+        mb.pop();
+        mb.pop();
+        assert!(mb.is_empty());
+        assert_eq!(mb.len(), 0);
+    }
+
+    #[test]
+    fn mailbox_push_pop_interleaved() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        mb.push(1);
+        mb.push(2);
+        assert_eq!(mb.pop(), Some(1));
+        mb.push(3);
+        assert_eq!(mb.pop(), Some(2));
+        assert_eq!(mb.pop(), Some(3));
+        assert_eq!(mb.pop(), None);
+    }
+
+    #[test]
+    fn drain_count_empty() {
+        let mb: Mailbox<u64> = Mailbox::new(10);
+        assert_eq!(mb.drain_count(), 0);
+    }
+
+    #[test]
+    fn drain_count_below_waterlevel() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        for i in 0..5 {
+            mb.push(i);
+        }
+        assert_eq!(mb.drain_count(), 5);
+    }
+
+    #[test]
+    fn drain_count_at_waterlevel_minus_one() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        for i in 0..9 {
+            mb.push(i);
+        }
+        // len=9 < waterlevel=10 → returns len
+        assert_eq!(mb.drain_count(), 9);
+    }
+
+    #[test]
+    fn drain_count_at_waterlevel() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        for i in 0..10 {
+            mb.push(i);
+        }
+        // len=10 >= waterlevel=10 → returns len >> 1 = 5
+        assert_eq!(mb.drain_count(), 5);
+    }
+
+    #[test]
+    fn drain_count_at_waterlevel_plus_one() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        for i in 0..11 {
+            mb.push(i);
+        }
+        // len=11 >= waterlevel=10 → returns 11 >> 1 = 5
+        assert_eq!(mb.drain_count(), 5);
+    }
+
+    #[test]
+    fn drain_count_well_above_waterlevel() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        for i in 0..100 {
+            mb.push(i);
+        }
+        // len=100 >= waterlevel=10 → returns 100 >> 1 = 50
+        assert_eq!(mb.drain_count(), 50);
+    }
+
+    #[test]
+    fn drain_count_odd_len_truncates() {
+        let mut mb: Mailbox<u64> = Mailbox::new(1);
+        for i in 0..7 {
+            mb.push(i);
+        }
+        // len=7 >= waterlevel=1 → returns 7 >> 1 = 3
+        assert_eq!(mb.drain_count(), 3);
+    }
+
+    #[test]
+    fn drain_count_waterlevel_one() {
+        let mut mb: Mailbox<u64> = Mailbox::new(1);
+        mb.push(42);
+        // len=1 >= waterlevel=1 → returns 1 >> 1 = 0
+        assert_eq!(mb.drain_count(), 0);
+    }
+
+    #[test]
+    fn drain_count_waterlevel_zero() {
+        // waterlevel=0 means len >= 0 is always true → always half-drain
+        let mb: Mailbox<u64> = Mailbox::new(0);
+        assert_eq!(mb.drain_count(), 0); // empty: 0 >> 1 = 0
+
+        let mut mb2: Mailbox<u64> = Mailbox::new(0);
+        mb2.push(1);
+        // len=1 >= waterlevel=0 → returns 1 >> 1 = 0
+        assert_eq!(mb2.drain_count(), 0);
+
+        let mut mb3: Mailbox<u64> = Mailbox::new(0);
+        mb3.push(1);
+        mb3.push(2);
+        // len=2 >= waterlevel=0 → returns 2 >> 1 = 1
+        assert_eq!(mb3.drain_count(), 1);
+    }
+
+    #[test]
+    fn drain_count_does_not_mutate() {
+        let mut mb: Mailbox<u64> = Mailbox::new(10);
+        for i in 0..5 {
+            mb.push(i);
+        }
+        let dc1 = mb.drain_count();
+        let dc2 = mb.drain_count();
+        assert_eq!(dc1, dc2);
+        assert_eq!(mb.len(), 5);
+    }
+
+    #[test]
+    fn drain_count_large_waterlevel() {
+        let mut mb: Mailbox<u64> = Mailbox::new(usize::MAX);
+        for i in 0..100 {
+            mb.push(i);
+        }
+        // len=100 < waterlevel=usize::MAX → always full drain
+        assert_eq!(mb.drain_count(), 100);
+    }
+
+    #[test]
+    fn mailbox_with_struct_messages() {
+        let mut mb: Mailbox<TestMsg> = Mailbox::new(10);
+        mb.push(TestMsg(1));
+        mb.push(TestMsg(2));
+        assert_eq!(mb.pop(), Some(TestMsg(1)));
+        assert_eq!(mb.pop(), Some(TestMsg(2)));
+        assert!(mb.is_empty());
+    }
+
+    // ── ActorPool tests ─────────────────────────────────────────────────
+
+    #[test]
+    fn pool_new_is_empty() {
+        let pool = ActorPool::new();
+        assert_eq!(pool.len(), 0);
+    }
+
+    #[test]
+    fn pool_insert_increments_len() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(1);
+        let (actor, _) = make_test_actor(addr, 100);
+        pool.insert(addr, actor);
+        assert_eq!(pool.len(), 1);
+
+        let addr2 = make_addr(2);
+        let (actor2, _) = make_test_actor(addr2, 100);
+        pool.insert(addr2, actor2);
+        assert_eq!(pool.len(), 2);
+    }
+
+    #[test]
+    fn pool_remove_returns_actor() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(1);
+        let (actor, _) = make_test_actor(addr, 100);
+        pool.insert(addr, actor);
+        assert!(pool.remove(&addr).is_some());
+        assert_eq!(pool.len(), 0);
+    }
+
+    #[test]
+    fn pool_remove_unknown_returns_none() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(99);
+        assert!(pool.remove(&addr).is_none());
+    }
+
+    #[test]
+    fn pool_deliver_correct_type() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(1);
+        let (actor, _) = make_test_actor(addr, 100);
+        pool.insert(addr, actor);
+
+        let msg: Box<dyn Any + Send> = Box::new(42u64);
+        assert!(pool.deliver(&addr, msg));
+    }
+
+    #[test]
+    fn pool_deliver_unknown_addr() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(99);
+        let msg: Box<dyn Any + Send> = Box::new(42u64);
+        assert!(!pool.deliver(&addr, msg));
+    }
+
+    #[test]
+    fn pool_deliver_wrong_type() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(1);
+        let (actor, _) = make_test_actor(addr, 100);
+        pool.insert(addr, actor);
+
+        // Actor expects u64, we send String
+        let msg: Box<dyn Any + Send> = Box::new("wrong type".to_string());
+        assert!(!pool.deliver(&addr, msg));
+    }
+
+    #[test]
+    fn pool_tick_all_processes_messages() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(1);
+        let (actor, counter) = make_test_actor(addr, 100);
+        pool.insert(addr, actor);
+
+        // Deliver 3 messages
+        pool.deliver(&addr, Box::new(1u64));
+        pool.deliver(&addr, Box::new(2u64));
+        pool.deliver(&addr, Box::new(3u64));
+
+        let stub = StubContextInner { waterlevel: 100 };
+        let did_work = pool.tick_all(&stub);
+        assert!(did_work);
+        assert_eq!(counter.load(Ordering::Relaxed), 3);
+    }
+
+    #[test]
+    fn pool_tick_all_empty_returns_false() {
+        let mut pool = ActorPool::new();
+        let addr = make_addr(1);
+        let (actor, _) = make_test_actor(addr, 100);
+        pool.insert(addr, actor);
+
+        // No messages delivered
+        let stub = StubContextInner { waterlevel: 100 };
+        let did_work = pool.tick_all(&stub);
+        assert!(!did_work);
+    }
+
+    // ── Worker tests ────────────────────────────────────────────────────
+
+    #[test]
+    fn worker_tick_once_no_work() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx],
+            spawn_txs: &[spawn_tx],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        assert!(!worker.tick_once(&tc));
+    }
+
+    #[test]
+    fn worker_tick_once_drains_spawns() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+
+        let addr = make_addr(1);
+        let (actor, _) = make_test_actor(addr, 100);
+        spawn_tx.try_send((addr, actor)).ok().unwrap();
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx],
+            spawn_txs: &[spawn_tx],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        assert!(worker.tick_once(&tc));
+        assert_eq!(worker.pool.len(), 1);
+    }
+
+    #[test]
+    fn worker_tick_once_drains_transfers() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let transfer_tx2 = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+        let spawn_tx2 = spawn_rx.new_sender();
+
+        let addr = make_addr(1);
+        let (actor, counter) = make_test_actor(addr, 100);
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+
+        // Spawn the actor first
+        spawn_tx.try_send((addr, actor)).ok().unwrap();
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx2],
+            spawn_txs: &[spawn_tx2],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        worker.tick_once(&tc); // drain spawns
+
+        // Now send a transfer envelope
+        let envelope = Envelope::new(addr, Box::new(42u64));
+        transfer_tx.try_send(envelope).ok().unwrap();
+
+        // Tick again to drain transfers + tick actors
+        let did_work = worker.tick_once(&tc);
+        assert!(did_work);
+        assert_eq!(counter.load(Ordering::Relaxed), 1);
+    }
+
+    #[test]
+    fn worker_tick_once_processes_messages() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let transfer_tx2 = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+        let spawn_tx2 = spawn_rx.new_sender();
+
+        let addr = make_addr(1);
+        let (actor, counter) = make_test_actor(addr, 100);
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+
+        spawn_tx.try_send((addr, actor)).ok().unwrap();
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx2],
+            spawn_txs: &[spawn_tx2],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        worker.tick_once(&tc); // spawn
+
+        // Deliver multiple messages
+        for i in 0..5u64 {
+            transfer_tx
+                .try_send(Envelope::new(addr, Box::new(i)))
+                .ok()
+                .unwrap();
+        }
+
+        worker.tick_once(&tc); // transfer + tick
+        assert_eq!(counter.load(Ordering::Relaxed), 5);
+    }
+
+    #[test]
+    fn worker_tick_once_multiple_spawns() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+
+        for i in 0..5u8 {
+            let addr = make_addr(i);
+            let (actor, _) = make_test_actor(addr, 100);
+            spawn_tx.try_send((addr, actor)).ok().unwrap();
+        }
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx],
+            spawn_txs: &[spawn_tx],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        assert!(worker.tick_once(&tc));
+        assert_eq!(worker.pool.len(), 5);
+    }
+
+    #[test]
+    fn worker_tick_once_wrong_type_no_panic() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let transfer_tx2 = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+        let spawn_tx2 = spawn_rx.new_sender();
+
+        let addr = make_addr(1);
+        let (actor, counter) = make_test_actor(addr, 100);
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+
+        spawn_tx.try_send((addr, actor)).ok().unwrap();
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx2],
+            spawn_txs: &[spawn_tx2],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        worker.tick_once(&tc); // spawn
+
+        // Send wrong type (String instead of u64) — should not panic
+        let bad_envelope = Envelope::new(addr, Box::new("wrong".to_string()));
+        transfer_tx.try_send(bad_envelope).ok().unwrap();
+
+        // Send correct type after
+        let good_envelope = Envelope::new(addr, Box::new(99u64));
+        transfer_tx.try_send(good_envelope).ok().unwrap();
+
+        worker.tick_once(&tc); // transfer + tick
+        // The correct message should still be processed
+        assert_eq!(counter.load(Ordering::Relaxed), 1);
+    }
+
+    #[test]
+    fn worker_run_stops_on_signal() {
+        let transfer_rx = Receiver::<Envelope>::new(64);
+        let spawn_rx = Receiver::<(ActorAddress, Box<dyn AnyActor>)>::new(64);
+
+        let transfer_tx = transfer_rx.new_sender();
+        let spawn_tx = spawn_rx.new_sender();
+
+        let mut worker = Worker::new(WorkerId(0), transfer_rx, spawn_rx);
+        let is_running = AtomicBool::new(false); // start as false → should exit immediately
+        let backoff = BackoffPolicy::default();
+
+        let address_map = AddressMap::new();
+        let placement = Placement::new(1);
+        let inbox_registry = InboxRegistry::new();
+        let config = RuntimeConfig::default();
+
+        let tc = TickContext {
+            address_map: &address_map,
+            transfer_txs: &[transfer_tx],
+            spawn_txs: &[spawn_tx],
+            placement: &placement,
+            inbox_registry: &inbox_registry,
+            config: &config,
+        };
+
+        // Run in a scoped thread to verify it actually terminates
+        thread::scope(|s| {
+            s.spawn(|| {
+                worker.run(&tc, &is_running, &backoff);
+            });
+        });
+        // If we get here, the thread exited — test passes
+    }
+}
+