Fix stdin stalls and test warnings

tests/test_poller.py

@@ -136,3 +136,36 @@ class TestPoller:
         # Queues should have None
         assert q1.get_nowait() is None
         assert q2.get_nowait() is None
+
+    @pytest.mark.asyncio
+    async def test_write_with_timeout_returns_true_on_success(self):
+        """write_with_timeout returns True when write completes."""
+        poller = Poller()
+        poller._loop = asyncio.get_event_loop()
+
+        with patch.object(poller._selector, "register"):
+            poller.add_file(42)
+
+        async def instant_write(fd, data):
+            # Simulate immediate completion
+            pass
+
+        with patch.object(poller, "write", side_effect=instant_write):
+            result = await poller.write_with_timeout(42, b"test", timeout=1.0)
+        assert result is True
+
+    @pytest.mark.asyncio
+    async def test_write_with_timeout_returns_false_on_timeout(self):
+        """write_with_timeout returns False when write times out."""
+        poller = Poller()
+        poller._loop = asyncio.get_event_loop()
+
+        with patch.object(poller._selector, "register"):
+            poller.add_file(42)
+
+        async def slow_write(fd, data):
+            await asyncio.sleep(999)
+
+        with patch.object(poller, "write", side_effect=slow_write):
+            result = await poller.write_with_timeout(42, b"test", timeout=0.01)
+        assert result is False