add failing test for cooperative concurrency

as provided by @SilverMira in #70, and tracked in #73

Co-authored-by: SilverMira <66930495+SilverMira@users.noreply.github.com>

Author: pchickey

Cargo.toml

@@ -32,6 +32,7 @@ serde_json = { workspace = true, optional = true }
 anyhow.workspace = true
 clap.workspace = true
 futures-lite.workspace = true
+futures-concurrency.workspace = true
 humantime.workspace = true
 serde = { workspace = true, features = ["derive"] }
 serde_json.workspace = true
@@ -63,6 +64,7 @@ cargo_metadata = "0.18.1"
 clap = { version = "4.5.26", features = ["derive"] }
 futures-core = "0.3.19"
 futures-lite = "1.12.0"
+futures-concurrency = "7.6"
 humantime = "2.1.0"
 heck = "0.5"
 http = "1.1"

src/runtime/reactor.rs

@@ -321,4 +321,31 @@ mod test {
             );
         })
     }
+
+    #[test]
+    fn cooperative_concurrency() {
+        crate::runtime::block_on(async {
+            let cpu_heavy = async move {
+                // Simulating a CPU-heavy task that runs for 1 second and yields occasionally
+                for _ in 0..10 {
+                    std::thread::sleep(std::time::Duration::from_millis(100));
+                    futures_lite::future::yield_now().await;
+                }
+                true
+            };
+            let timeout = async move {
+                crate::time::Timer::after(crate::time::Duration::from_millis(200))
+                    .wait()
+                    .await;
+                false
+            };
+            let mut future_group = futures_concurrency::future::FutureGroup::<
+                Pin<Box<dyn std::future::Future<Output = bool>>>,
+            >::new();
+            future_group.insert(Box::pin(cpu_heavy));
+            future_group.insert(Box::pin(timeout));
+            let result = futures_lite::StreamExt::next(&mut future_group).await;
+            assert_eq!(result, Some(false), "cpu_heavy task should have timed out");
+        });
+    }
 }