Elaborate on BindStream tests

src/runtime/bind_stream.rs

@@ -138,40 +138,24 @@ mod tests {
     use super::*;
 
     #[test]
-    fn pending_without_change() {
-        use futures::{
-            executor::{block_on, LocalPool},
-            stream::StreamExt,
-            task::LocalSpawnExt,
-        };
-
-        let mut brt = BindStream::new(|| ());
-        block_on(brt.next()).expect("BindStream should yield first revision immediately");
-        let mut pool = LocalPool::new();
-        pool.spawner()
-            .spawn_local(async move {
-                brt.next().await.unwrap();
-                unreachable!()
-            })
-            .unwrap();
-        assert!(!pool.try_run_one());
-    }
+    fn behavior_on_state_change() {
+        let (mut brt, key) = BindStream::init(|| crate::state(|| 0).1);
 
-    #[test]
-    fn has_changes() {
-        use futures::{executor::LocalPool, task::LocalSpawnExt};
+        // state after initialization
+        assert!(brt.try_next().is_none());
 
-        let (mut brt, key) = BindStream::init(|| crate::state(|| 0).1);
-        let mut pool = LocalPool::new();
-        pool.spawner()
-            .spawn_local(async move {
-                brt.next().await;
-            })
-            .unwrap();
-        assert!(!pool.try_run_one());
+        // no actual change in value
         key.set(0);
-        assert!(!pool.try_run_one());
+        assert!(brt.try_next().is_none());
+
+        // actual change in value
         key.set(1);
-        assert!(pool.try_run_one());
+        assert!(brt.try_next().is_some());
+
+        // two changes in one revision
+        key.set(2);
+        key.set(3);
+        assert!(brt.try_next().is_some());
+        assert!(brt.try_next().is_none());
     }
 }