test: cover initialize protocol mismatch response

Author: he-yufeng

tests/shared/test_streamable_http.py

@@ -26,6 +26,7 @@
 from starlette.applications import Starlette
 from starlette.requests import Request
 from starlette.routing import Mount
+from starlette.types import Message
 
 from mcp import MCPError, types
 from mcp.client.session import ClientSession
@@ -1755,6 +1756,67 @@ def test_server_rejects_initialize_protocol_version_mismatch(
     assert "protocolVersion" in response.text
 
 
+@pytest.mark.anyio
+async def test_server_rejects_initialize_protocol_version_mismatch_in_process():
+    transport = StreamableHTTPServerTransport("/mcp")
+    write_stream, read_stream = create_context_streams[SessionMessage | Exception](1)
+    transport._read_stream_writer = write_stream
+    body = json.dumps(
+        {
+            "jsonrpc": "2.0",
+            "method": "initialize",
+            "params": {
+                "clientInfo": {"name": "test-client", "version": "1.0"},
+                "protocolVersion": "2025-06-18",
+                "capabilities": {},
+            },
+            "id": "init-1",
+        }
+    ).encode()
+    sent: list[Message] = []
+    received_body = False
+
+    async def receive() -> Message:
+        nonlocal received_body
+        if received_body:
+            return {"type": "http.disconnect"}
+
+        received_body = True
+        return {"type": "http.request", "body": body, "more_body": False}
+
+    async def send(message: Message) -> None:
+        sent.append(message)
+
+    scope = {
+        "type": "http",
+        "asgi": {"version": "3.0"},
+        "method": "POST",
+        "path": "/mcp",
+        "raw_path": b"/mcp",
+        "query_string": b"",
+        "headers": [
+            (b"accept", b"application/json, text/event-stream"),
+            (b"content-type", b"application/json"),
+            (MCP_PROTOCOL_VERSION_HEADER.encode(), b"2025-03-26"),
+        ],
+        "client": ("testclient", 50000),
+        "server": ("testserver", 80),
+        "scheme": "http",
+    }
+
+    try:
+        await transport.handle_request(scope, receive, send)
+        assert await receive() == {"type": "http.disconnect"}
+    finally:
+        await write_stream.aclose()
+        await read_stream.aclose()
+
+    assert any(message["type"] == "http.response.start" and message["status"] == 400 for message in sent)
+    response_body = b"".join(message.get("body", b"") for message in sent if message["type"] == "http.response.body")
+    assert MCP_PROTOCOL_VERSION_HEADER.encode() in response_body
+    assert b"protocolVersion" in response_body
+
+
 def test_server_backwards_compatibility_no_protocol_version(basic_server: None, basic_server_url: str):
     """Test server accepts requests without protocol version header."""
     # First initialize a session to get a valid session ID