Restore full coverage after the BaseSession deletion

Covers MCPError.from_jsonrpc_error and the context-stream sync close()
methods, whose only exercisers died with BaseSession and its tests, and
restructures three test handler arms that could never take their false
branch.

Author: maxisbey

tests/client/test_session.py

@@ -875,8 +875,9 @@ async def boom(progress: float, total: float | None, message: str | None) -> Non
         raise RuntimeError("progress boom")
 
     async def handler(msg: object) -> None:
-        if isinstance(msg, types.ProgressNotification):
-            delivered.set()
+        # Only the progress notification is teed to the message handler here.
+        assert isinstance(msg, types.ProgressNotification)
+        delivered.set()
 
     async with raw_client_session(message_handler=handler) as (session, to_client, from_client):
         async with anyio.create_task_group() as tg:

tests/interaction/lowlevel/test_cancellation.py

@@ -268,10 +268,8 @@ def respond(request_id: types.RequestId, result: types.Result) -> SessionMessage
         await server_write.send(respond(9999, EmptyResult()))
         await server_write.send(respond(ping.message.id, EmptyResult()))
 
-    incoming: list[IncomingMessage] = []
-
     async def message_handler(message: IncomingMessage) -> None:
-        incoming.append(message)
+        raise NotImplementedError  # unreachable: nothing is surfaced for an unknown-id response
 
     async with (
         create_client_server_memory_streams() as ((client_read, client_write), server_streams),
@@ -285,5 +283,4 @@ async def message_handler(message: IncomingMessage) -> None:
 
         assert pong == snapshot(EmptyResult())
         # The fabricated response was dropped silently: the ping after it still
-        # round-tripped, and nothing was surfaced to the message handler.
-        assert incoming == []
+        # round-tripped, and the message handler (a tripwire) was never invoked.

tests/shared/test_context_streams.py

@@ -0,0 +1,20 @@
+"""Tests for the contextvars-carrying memory-stream wrappers."""
+
+import anyio
+import pytest
+
+from mcp.shared._context_streams import create_context_streams
+
+pytestmark = pytest.mark.anyio
+
+
+async def test_sync_close_closes_the_underlying_streams() -> None:
+    """The wrappers mirror anyio's memory streams: close() is the sync form of aclose()."""
+    send, receive = create_context_streams[str](1)
+    await send.send("queued")
+    send.close()
+    receive.close()
+    with pytest.raises(anyio.ClosedResourceError):
+        await send.send("after close")
+    with pytest.raises(anyio.ClosedResourceError):
+        await receive.receive()

tests/shared/test_exceptions.py

@@ -3,7 +3,7 @@
 import pytest
 
 from mcp.shared.exceptions import MCPError, UrlElicitationRequiredError
-from mcp.types import URL_ELICITATION_REQUIRED, ElicitRequestURLParams, ErrorData
+from mcp.types import URL_ELICITATION_REQUIRED, ElicitRequestURLParams, ErrorData, JSONRPCError
 
 
 def test_url_elicitation_required_error_create_with_single_elicitation() -> None:
@@ -162,3 +162,14 @@ def test_url_elicitation_required_error_exception_message() -> None:
 
     # The exception's string representation should match the message
     assert str(error) == "URL elicitation required"
+
+
+def test_from_jsonrpc_error_preserves_code_message_and_data() -> None:
+    """Building an MCPError from a wire JSONRPCError keeps every error field."""
+    wire = JSONRPCError(
+        jsonrpc="2.0",
+        id=3,
+        error=ErrorData(code=URL_ELICITATION_REQUIRED, message="go elsewhere", data={"hint": "y"}),
+    )
+    error = MCPError.from_jsonrpc_error(wire)
+    assert error.error == ErrorData(code=URL_ELICITATION_REQUIRED, message="go elsewhere", data={"hint": "y"})

tests/shared/test_streamable_http.py

@@ -2247,8 +2247,9 @@ async def test_standalone_stream_teardown_mid_listen_is_not_an_error(caplog: pyt
     async def message_handler(
         message: RequestResponder[types.ServerRequest, types.ClientResult] | types.ServerNotification | Exception,
     ) -> None:
-        if isinstance(message, types.ResourceUpdatedNotification):
-            notified.set()
+        # Only the standalone-stream notification is teed to the handler here.
+        assert isinstance(message, types.ResourceUpdatedNotification)
+        notified.set()
 
     async with session_manager.run():
         async with (