tests for issue 88

tests/issues/test_88_random_error.py

@@ -0,0 +1,100 @@
+"""Test to reproduce issue #88: Random error thrown on response."""
+
+from datetime import timedelta
+from pathlib import Path
+from typing import Sequence
+
+import anyio
+import pytest
+
+from mcp.client.session import ClientSession
+from mcp.server.lowlevel import Server
+from mcp.shared.exceptions import McpError
+from mcp.types import (
+    EmbeddedResource,
+    ImageContent,
+    TextContent,
+)
+
+
+@pytest.mark.anyio
+async def test_notification_validation_error(tmp_path: Path):
+    """Test that timeouts are handled gracefully and don't break the server.
+
+    This test verifies that when a client request times out:
+    1. The server task stays alive
+    2. The server can still handle new requests
+    3. The client can make new requests
+    4. No resources are leaked
+    """
+
+    server = Server(name="test")
+    request_count = 0
+    slow_request_complete = False
+
+    @server.call_tool()
+    async def slow_tool(
+        name: str, arg
+    ) -> Sequence[TextContent | ImageContent | EmbeddedResource]:
+        nonlocal request_count, slow_request_complete
+        request_count += 1
+
+        if name == "slow":
+            # Long enough to ensure timeout
+            await anyio.sleep(0.2)
+            slow_request_complete = True
+            return [TextContent(type="text", text=f"slow {request_count}")]
+        elif name == "fast":
+            # Fast enough to complete before timeout
+            await anyio.sleep(0.01)
+            return [TextContent(type="text", text=f"fast {request_count}")]
+        return [TextContent(type="text", text=f"unknown {request_count}")]
+
+    async def server_handler(read_stream, write_stream):
+        await server.run(
+            read_stream,
+            write_stream,
+            server.create_initialization_options(),
+            raise_exceptions=True,
+        )
+
+    async def client(read_stream, write_stream):
+        # Use a timeout that's:
+        # - Long enough for fast operations (>10ms)
+        # - Short enough for slow operations (<200ms)
+        # - Not too short to avoid flakiness
+        async with ClientSession(
+            read_stream, write_stream, read_timeout_seconds=timedelta(milliseconds=50)
+        ) as session:
+            await session.initialize()
+
+            # First call should work (fast operation)
+            result = await session.call_tool("fast")
+            assert result.content == [TextContent(type="text", text="fast 1")]
+            assert not slow_request_complete
+
+            # Second call should timeout (slow operation)
+            with pytest.raises(McpError) as exc_info:
+                await session.call_tool("slow")
+            assert "Timed out while waiting" in str(exc_info.value)
+
+            # Wait for slow request to complete in the background
+            await anyio.sleep(0.3)
+            assert slow_request_complete
+
+            # Third call should work (fast operation),
+            # proving server is still responsive
+            result = await session.call_tool("fast")
+            assert result.content == [TextContent(type="text", text="fast 3")]
+
+    # Run server and client in separate task groups to avoid cancellation
+    server_writer, server_reader = anyio.create_memory_object_stream(1)
+    client_writer, client_reader = anyio.create_memory_object_stream(1)
+
+    async with anyio.create_task_group() as tg:
+        tg.start_soon(server_handler, server_reader, client_writer)
+        # Wait for server to start and initialize
+        await anyio.sleep(0.1)
+        # Run client in a separate task to avoid cancellation
+        async with anyio.create_task_group() as client_tg:
+            client_tg.start_soon(client, client_reader, server_writer)