sync: adds Notify for basic task notification (#2210)

`Notify` provides a synchronization primitive similar to thread park /
unpark, except for tasks.

1 files changed, 102 insertions, 0 deletions

diff --git a/tokio/tests/sync_notify.rs b/tokio/tests/sync_notify.rs
new file mode 100644
index 00000000..be39ce32
--- /dev/null
+++ b/tokio/tests/sync_notify.rs
@@ -0,0 +1,102 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+
+use tokio::sync::Notify;
+use tokio_test::task::spawn;
+use tokio_test::*;
+
+trait AssertSend: Send + Sync {}
+impl AssertSend for Notify {}
+
+#[test]
+fn notify_notified_one() {
+    let notify = Notify::new();
+    let mut notified = spawn(async { notify.notified().await });
+
+    notify.notify();
+    assert_ready!(notified.poll());
+}
+
+#[test]
+fn notified_one_notify() {
+    let notify = Notify::new();
+    let mut notified = spawn(async { notify.notified().await });
+
+    assert_pending!(notified.poll());
+
+    notify.notify();
+    assert!(notified.is_woken());
+    assert_ready!(notified.poll());
+}
+
+#[test]
+fn notified_multi_notify() {
+    let notify = Notify::new();
+    let mut notified1 = spawn(async { notify.notified().await });
+    let mut notified2 = spawn(async { notify.notified().await });
+
+    assert_pending!(notified1.poll());
+    assert_pending!(notified2.poll());
+
+    notify.notify();
+    assert!(notified1.is_woken());
+    assert!(!notified2.is_woken());
+
+    assert_ready!(notified1.poll());
+    assert_pending!(notified2.poll());
+}
+
+#[test]
+fn notify_notified_multi() {
+    let notify = Notify::new();
+
+    notify.notify();
+
+    let mut notified1 = spawn(async { notify.notified().await });
+    let mut notified2 = spawn(async { notify.notified().await });
+
+    assert_ready!(notified1.poll());
+    assert_pending!(notified2.poll());
+
+    notify.notify();
+
+    assert!(notified2.is_woken());
+    assert_ready!(notified2.poll());
+}
+
+#[test]
+fn notified_drop_notified_notify() {
+    let notify = Notify::new();
+    let mut notified1 = spawn(async { notify.notified().await });
+    let mut notified2 = spawn(async { notify.notified().await });
+
+    assert_pending!(notified1.poll());
+
+    drop(notified1);
+
+    assert_pending!(notified2.poll());
+
+    notify.notify();
+    assert!(notified2.is_woken());
+    assert_ready!(notified2.poll());
+}
+
+#[test]
+fn notified_multi_notify_drop_one() {
+    let notify = Notify::new();
+    let mut notified1 = spawn(async { notify.notified().await });
+    let mut notified2 = spawn(async { notify.notified().await });
+
+    assert_pending!(notified1.poll());
+    assert_pending!(notified2.poll());
+
+    notify.notify();
+
+    assert!(notified1.is_woken());
+    assert!(!notified2.is_woken());
+
+    drop(notified1);
+
+    assert!(notified2.is_woken());
+    assert_ready!(notified2.poll());
+}