chore: import upstream snapshot with attribution

tests/shared/conftest.py

@@ -0,0 +1,61 @@
+"""Shared fixtures for `Dispatcher` contract tests.
+
+The `pair_factory` fixture parametrizes contract tests over every `Dispatcher`
+implementation, so the same behavioral assertions run against `DirectDispatcher`
+(in-memory) and `JSONRPCDispatcher` (over crossed anyio memory streams).
+"""
+
+from collections.abc import Callable
+
+import anyio
+import pytest
+
+from mcp.shared.direct_dispatcher import create_direct_dispatcher_pair
+from mcp.shared.dispatcher import Dispatcher
+from mcp.shared.jsonrpc_dispatcher import JSONRPCDispatcher
+from mcp.shared.message import SessionMessage
+from mcp.shared.transport_context import TransportContext
+
+DispatcherTriple = tuple[Dispatcher[TransportContext], Dispatcher[TransportContext], Callable[[], None]]
+PairFactory = Callable[..., DispatcherTriple]
+
+
+def direct_pair(*, can_send_request: bool = True) -> DispatcherTriple:
+    client, server = create_direct_dispatcher_pair(can_send_request=can_send_request)
+
+    def close() -> None:
+        client.close()
+        server.close()
+
+    return client, server, close
+
+
+def jsonrpc_pair(*, can_send_request: bool = True) -> DispatcherTriple:
+    """Two `JSONRPCDispatcher`s wired over crossed in-memory streams."""
+    c2s_send, c2s_recv = anyio.create_memory_object_stream[SessionMessage | Exception](32)
+    s2c_send, s2c_recv = anyio.create_memory_object_stream[SessionMessage | Exception](32)
+
+    def builder(_meta: object) -> TransportContext:
+        return TransportContext(kind="jsonrpc", can_send_request=can_send_request)
+
+    client: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher(s2c_recv, c2s_send, transport_builder=builder)
+    server: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher(c2s_recv, s2c_send, transport_builder=builder)
+
+    def close() -> None:
+        for s in (c2s_send, c2s_recv, s2c_send, s2c_recv):
+            s.close()
+
+    return client, server, close
+
+
+@pytest.fixture(
+    params=[
+        pytest.param(direct_pair, id="direct"),
+        pytest.param(jsonrpc_pair, id="jsonrpc"),
+    ]
+)
+def pair_factory(request: pytest.FixtureRequest) -> PairFactory:
+    return request.param
+
+
+__all__ = ["PairFactory", "direct_pair", "jsonrpc_pair"]