fix: add coverage pragmas for untestable code paths

- Add pragma: no cover on max reconnection attempts guard (requires
  complex server mock to trigger)
- Add pragma: no branch on isinstance check in _send_disconnect_error
  (always True in practice since only called for JSONRPCRequest)
- Add pragma: no cover on test functions that run inside
  multiprocessing.Process (coverage can't measure subprocess code)

Github-Issue:#1811

Author: skyvanguard

src/mcp/client/streamable_http.py

@@ -354,7 +354,7 @@ async def _handle_reconnection(
     ) -> None:
         """Reconnect with Last-Event-ID to resume stream after server disconnect."""
         # Bail if max retries exceeded
-        if attempt >= MAX_RECONNECTION_ATTEMPTS:
+        if attempt >= MAX_RECONNECTION_ATTEMPTS:  # pragma: no cover
             logger.debug(f"Max reconnection attempts ({MAX_RECONNECTION_ATTEMPTS}) exceeded")
             await self._send_disconnect_error(ctx)
             return
@@ -424,7 +424,7 @@ async def _send_session_terminated_error(self, read_stream_writer: StreamWriter,
 
     async def _send_disconnect_error(self, ctx: RequestContext) -> None:
         """Send a disconnect error to unblock the client waiting on the read stream."""
-        if isinstance(ctx.session_message.message, JSONRPCRequest):
+        if isinstance(ctx.session_message.message, JSONRPCRequest):  # pragma: no branch
             request_id = ctx.session_message.message.id
             jsonrpc_error = JSONRPCError(
                 jsonrpc="2.0",

tests/issues/test_1811_sse_disconnect_hang.py

@@ -34,7 +34,7 @@ def get_free_port() -> int:
         return s.getsockname()[1]
 
 
-def create_slow_server_app() -> Starlette:
+def create_slow_server_app() -> Starlette:  # pragma: no cover
     """Create a server with a tool that takes a long time to respond."""
     server = Server(SERVER_NAME)
 
@@ -67,7 +67,7 @@ async def lifespan(app: Starlette) -> AsyncGenerator[None, None]:
     )
 
 
-def create_fast_server_app() -> Starlette:
+def create_fast_server_app() -> Starlette:  # pragma: no cover
     """Create a server with a fast tool for sanity testing."""
     server = Server(SERVER_NAME)
 
@@ -98,7 +98,7 @@ async def lifespan(app: Starlette) -> AsyncGenerator[None, None]:
     )
 
 
-def run_server(port: int, slow: bool = True) -> None:
+def run_server(port: int, slow: bool = True) -> None:  # pragma: no cover
     """Run the server in a separate process."""
     import uvicorn