Add a first receiver is cancelled test

tests/test_task_broadcasting.py

@@ -416,3 +416,44 @@ def test_ensure_slow_consumers_lag_out(
                 await brx.aclose()
 
     trio.run(main)
+
+
+def test_first_recver_is_cancelled():
+
+    async def main():
+
+        # make sure it all works within the runtime
+        async with tractor.open_root_actor():
+
+            tx, rx = trio.open_memory_channel(1)
+            brx = broadcast_receiver(rx, 1)
+            cs = trio.CancelScope()
+            sequence = list(range(3))
+
+            async def sub_and_recv():
+                with cs:
+                    async with brx.subscribe() as bc:
+                        async for value in bc:
+                            print(value)
+
+            async def cancel_and_send():
+                await trio.sleep(0.2)
+                cs.cancel()
+                await tx.send(1)
+
+            async with trio.open_nursery() as n:
+
+                n.start_soon(sub_and_recv)
+                await trio.sleep(0.1)
+                assert brx._state.recv_ready
+
+                n.start_soon(cancel_and_send)
+
+                # ensure that we don't hang because no-task is now
+                # waiting on the underlying receive..
+                with trio.fail_after(0.5):
+                    value = await brx.receive()
+                    print(f'parent: {value}')
+                    assert value == 1
+
+    trio.run(main)