test(telegram): cover local attachment filenames

Add a regression test for preserving the original basename when Telegram sends local media bytes.

Made-with: Cursor

tests/channels/test_telegram_channel.py

@@ -1,4 +1,3 @@
-import asyncio
 from pathlib import Path
 from types import SimpleNamespace
 from unittest.mock import AsyncMock
@@ -13,8 +12,12 @@ except ImportError:
 
 from nanobot.bus.events import OutboundMessage
 from nanobot.bus.queue import MessageBus
-from nanobot.channels.telegram import TELEGRAM_REPLY_CONTEXT_MAX_LEN, TelegramChannel, _StreamBuf
+from nanobot.channels.telegram import (
-from nanobot.channels.telegram import TelegramConfig
+    TELEGRAM_REPLY_CONTEXT_MAX_LEN,
+    TelegramChannel,
+    TelegramConfig,
+    _StreamBuf,
+)
 
 
 class _FakeHTTPXRequest:
@@ -752,6 +755,36 @@ async def test_send_remote_media_url_after_security_validation(monkeypatch) -> N
     ]
 
 
+@pytest.mark.asyncio
+async def test_send_local_media_preserves_filename(tmp_path: Path) -> None:
+    channel = TelegramChannel(
+        TelegramConfig(enabled=True, token="123:abc", allow_from=["*"]),
+        MessageBus(),
+    )
+    channel._app = _FakeApp(lambda: None)
+    attachment = tmp_path / "report.final.md"
+    attachment.write_bytes(b"# Report\n")
+
+    await channel.send(
+        OutboundMessage(
+            channel="telegram",
+            chat_id="123",
+            content="",
+            media=[str(attachment)],
+        )
+    )
+
+    assert channel._app.bot.sent_media == [
+        {
+            "kind": "document",
+            "chat_id": 123,
+            "document": b"# Report\n",
+            "reply_parameters": None,
+            "filename": "report.final.md",
+        }
+    ]
+
+
 @pytest.mark.asyncio
 async def test_send_blocks_unsafe_remote_media_url(monkeypatch) -> None:
     channel = TelegramChannel(