NOMERGE: Test that MemoryObjectSendStream.send_nowait() raises WouldBlock when called immediately after cancelling receive()

Author: gschaffner

Diff for: tests/streams/test_memory.py

@@ -15,6 +15,7 @@
     create_memory_object_stream,
     create_task_group,
     fail_after,
+    get_cancelled_exc_class,
     wait_all_tasks_blocked,
 )
 from anyio.abc import ObjectReceiveStream, ObjectSendStream, TaskStatus
@@ -326,34 +327,27 @@ async def scoped_receiver(task_status: TaskStatus[CancelScope]) -> None:
 
 async def test_cancel_during_receive_before_send_nowait() -> None:
     """
-    Test that cancelling a pending receive() operation does not cause an item about to
-    be placed into the stream by send_nowait() to be lost.
-
-    Note: AnyIO's memory stream behavior here currently differs slightly from Trio's
-    memory channel behavior. This test is intended only as a regression test for the bug
-    where AnyIO dropped items in this situation; addressing the (possible) issue where
-    AnyIO behaves slightly differently from Trio in this situation will involve
-    modifying this test. See #728.
+    Test that cancelling a pending receive() operation causes a send_nowait() call made
+    before the receive() call has raised to raise WouldBlock.
 
     """
 
     async def scoped_receiver(task_status: TaskStatus[CancelScope]) -> None:
         with CancelScope() as receiver_scope:
             task_status.started(receiver_scope)
-            received.append(await receive.receive())
+            with pytest.raises(get_cancelled_exc_class()):
+                await receive.receive()
 
         assert receiver_scope.cancel_called
 
-    received: list[str] = []
     send, receive = create_memory_object_stream[str]()
     with send, receive:
         async with create_task_group() as tg:
             receiver_scope = await tg.start(scoped_receiver)
             await wait_all_tasks_blocked()
             receiver_scope.cancel()
-            send.send_nowait("hello")
-
-        assert received == ["hello"]
+            with pytest.raises(WouldBlock):
+                send.send_nowait("hello")
 
 
 async def test_close_receive_after_send() -> None: