test: narrow websocket_server pragma now that coverage reaches it

The function-level pragma existed because the server ran in a subprocess
where coverage couldn't instrument it. The in-thread conversion makes it
reachable, so strict-no-cover (#2305) flags it as stale. Narrow the pragma
to the three error paths the smoke test doesn't exercise.

Author: maxisbey

src/mcp/server/websocket.py

@@ -10,7 +10,7 @@
 from mcp.shared.message import SessionMessage
 
 
-@asynccontextmanager  # pragma: no cover
+@asynccontextmanager
 async def websocket_server(scope: Scope, receive: Receive, send: Send):
     """WebSocket server transport for MCP. This is an ASGI application, suitable for use
     with a framework like Starlette and a server like Hypercorn.
@@ -34,13 +34,13 @@ async def ws_reader():
                 async for msg in websocket.iter_text():
                     try:
                         client_message = types.jsonrpc_message_adapter.validate_json(msg, by_name=False)
-                    except ValidationError as exc:
+                    except ValidationError as exc:  # pragma: no cover
                         await read_stream_writer.send(exc)
                         continue
 
                     session_message = SessionMessage(client_message)
                     await read_stream_writer.send(session_message)
-        except anyio.ClosedResourceError:
+        except anyio.ClosedResourceError:  # pragma: no cover
             await websocket.close()
 
     async def ws_writer():
@@ -49,7 +49,7 @@ async def ws_writer():
                 async for session_message in write_stream_reader:
                     obj = session_message.message.model_dump_json(by_alias=True, exclude_unset=True)
                     await websocket.send_text(obj)
-        except anyio.ClosedResourceError:
+        except anyio.ClosedResourceError:  # pragma: no cover
             await websocket.close()
 
     async with anyio.create_task_group() as tg:

tests/shared/test_ws.py

@@ -1,9 +1,9 @@
 """Smoke test for the WebSocket transport.
 
-Runs the full WS stack end-to-end over a real TCP connection to provide
-coverage of ``src/mcp/client/websocket.py``. MCP semantics (error
-propagation, timeouts, etc.) are transport-agnostic and are covered in
-``tests/client/test_client.py`` and ``tests/issues/test_88_random_error.py``.
+Runs the full WS stack end-to-end over a real TCP connection, covering both
+``src/mcp/client/websocket.py`` and ``src/mcp/server/websocket.py``. MCP
+semantics (error propagation, timeouts, etc.) are transport-agnostic and are
+covered in ``tests/client/test_client.py`` and ``tests/issues/test_88_random_error.py``.
 """
 
 from collections.abc import Generator