Add unittest sse disconnect

Author: Hoa Lam

tests/server/test_sse_disconnect.py

@@ -0,0 +1,54 @@
+import asyncio
+from uuid import UUID
+
+import pytest
+from starlette.types import Message, Scope
+
+from mcp.server.sse import SseServerTransport
+
+
+@pytest.mark.anyio
+async def test_sse_disconnect_handle():
+    transport = SseServerTransport(endpoint="/sse")
+    # Create a minimal ASGI scope for an HTTP GET request
+    scope: Scope = {
+        "type": "http",
+        "method": "GET",
+        "path": "/sse",
+        "headers": [],
+    }
+    send_disconnect = False
+
+    # Dummy receive and send functions
+    async def receive() -> dict:
+        nonlocal send_disconnect
+        if not send_disconnect:
+            send_disconnect = True
+            return {"type": "http.request"}
+        else:
+            return {"type": "http.disconnect"}
+
+    async def send(message: Message) -> None:
+        await asyncio.sleep(0)
+
+    # Run the connect_sse context manager
+    async with transport.connect_sse(scope, receive, send) as (
+        read_stream,
+        write_stream,
+    ):
+        # Assert that streams are provided
+        assert read_stream is not None
+        assert write_stream is not None
+
+        # There should be exactly one session
+        assert len(transport._read_stream_writers) == 1
+        # Check that the session key is a UUID
+        session_id = next(iter(transport._read_stream_writers.keys()))
+        assert isinstance(session_id, UUID)
+
+        # Check that the writer is still open
+        writer = transport._read_stream_writers[session_id]
+        assert writer is not None
+
+    # After context exits, session should be cleaned up
+    assert len(transport._read_stream_writers) == 0