task: Add MCP E2E tests

Author: neelay-aign

tests/aignostics/utils/TC-UTILS-MCP-01.feature

@@ -0,0 +1,15 @@
+Feature: MCP Server Plugin Auto-Discovery
+
+  The central MCP server discovers plugin tools registered via Python entry
+  points, mounts them with namespace isolation, and serves them to MCP clients.
+
+  @tests:SPEC-UTILS-SERVICE
+  @tests:SWR-UTILS-1-1
+  @id:TC-UTILS-MCP-01
+  Scenario: Server discovers plugin tools via entry points and serves them to a client
+    Given a plugin package registers an entry point under "aignostics.plugins"
+    And the plugin exposes a FastMCP instance with tools "dummy_echo" and "dummy_add"
+    When the MCP server is created via mcp_create_server()
+    And a client connects and lists tools
+    Then the tool list includes "dummy_plugin_dummy_echo" and "dummy_plugin_dummy_add"
+    And calling "dummy_plugin_dummy_echo" with message "hello" returns "hello"

tests/aignostics/utils/mcp_test.py

@@ -3,17 +3,26 @@
 from __future__ import annotations
 
 import asyncio
+import subprocess
+import sys
+from pathlib import Path
+from typing import TYPE_CHECKING
 from unittest.mock import patch
 
 import pytest
-from fastmcp import FastMCP
+from fastmcp import Client, FastMCP
 
 from aignostics.utils import (
     MCP_SERVER_NAME,
+    discover_plugin_packages,
     mcp_create_server,
     mcp_discover_servers,
     mcp_list_tools,
 )
+from aignostics.utils._di import _implementation_cache
+
+if TYPE_CHECKING:
+    from collections.abc import Iterator
 
 # Patch targets
 PATCH_LOCATE_IMPLEMENTATIONS = "aignostics.utils._mcp.locate_implementations"
@@ -175,3 +184,78 @@ def test_mcp_list_tools_empty(record_property) -> None:
         tools = mcp_list_tools()
         # Should return empty list when no plugins have tools
         assert tools == []
+
+
+# =============================================================================
+# E2E Plugin Auto-Discovery Tests
+# =============================================================================
+
+DUMMY_PLUGIN_DIR = Path(__file__).resolve().parents[2] / "resources" / "mcp_dummy_plugin"
+
+
+def _clear_mcp_discovery_caches() -> None:
+    """Invalidate DI and plugin caches so MCP discovery starts fresh."""
+    _implementation_cache.pop(FastMCP, None)
+    discover_plugin_packages.cache_clear()
+
+
+@pytest.fixture(scope="session")
+def install_dummy_mcp_plugin() -> Iterator[None]:
+    """Install the dummy MCP plugin in editable mode and make it importable.
+
+    Refreshes site-packages so the running interpreter sees the new package
+    and its entry points without a process restart.
+    """
+    import importlib
+    import site
+
+    subprocess.check_call(
+        [sys.executable, "-m", "pip", "install", "-e", str(DUMMY_PLUGIN_DIR)],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+    )
+
+    importlib.invalidate_caches()
+    for sp in site.getsitepackages():
+        site.addsitedir(sp)
+
+    yield
+
+    subprocess.check_call(
+        [sys.executable, "-m", "pip", "uninstall", "-y", "mcp-dummy-plugin"],
+        stdout=subprocess.DEVNULL,
+        stderr=subprocess.PIPE,
+    )
+
+
+@pytest.fixture
+def clear_mcp_caches() -> Iterator[None]:
+    """Clear MCP discovery caches before and after the test."""
+    _clear_mcp_discovery_caches()
+    yield
+    _clear_mcp_discovery_caches()
+
+
+@pytest.mark.e2e
+@pytest.mark.timeout(timeout=60)
+def test_mcp_server_discovers_and_serves_plugin_tools(
+    install_dummy_mcp_plugin, clear_mcp_caches, record_property
+) -> None:
+    """Full E2E: entry point registration -> discovery -> mount -> client round-trip."""
+    record_property("tested-item-id", "TC-UTILS-MCP-01")
+
+    server = mcp_create_server()
+    tool_names = list(asyncio.run(server.get_tools()).keys())
+
+    assert "dummy_plugin_dummy_echo" in tool_names
+    assert "dummy_plugin_dummy_add" in tool_names
+
+    async def _call_tools() -> tuple[str, str]:
+        async with Client(server) as client:
+            echo_result = await client.call_tool("dummy_plugin_dummy_echo", {"message": "hello"})
+            add_result = await client.call_tool("dummy_plugin_dummy_add", {"a": 2, "b": 3})
+            return echo_result.content[0].text, add_result.content[0].text
+
+    echo_text, add_text = asyncio.run(_call_tools())
+    assert echo_text == "hello"
+    assert add_text == "5"

tests/resources/mcp_dummy_plugin/pyproject.toml

@@ -0,0 +1,16 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "mcp-dummy-plugin"
+version = "0.0.1"
+description = "Dummy MCP plugin for E2E testing of plugin auto-discovery."
+requires-python = ">=3.11"
+dependencies = ["fastmcp>=2.0.0,<3"]
+
+[project.entry-points."aignostics.plugins"]
+mcp_dummy_plugin = "mcp_dummy_plugin"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/mcp_dummy_plugin"]

tests/resources/mcp_dummy_plugin/src/mcp_dummy_plugin/__init__.py

@@ -0,0 +1,5 @@
+"""Dummy MCP plugin for E2E testing of plugin auto-discovery."""
+
+from ._mcp import mcp
+
+__all__ = ["mcp"]

tests/resources/mcp_dummy_plugin/src/mcp_dummy_plugin/_mcp.py

@@ -0,0 +1,17 @@
+"""Dummy MCP tools for E2E testing."""
+
+from fastmcp import FastMCP
+
+mcp = FastMCP("dummy_plugin")
+
+
+@mcp.tool
+def dummy_echo(message: str) -> str:
+    """Echo the provided message back."""
+    return message
+
+
+@mcp.tool
+def dummy_add(a: int, b: int) -> str:
+    """Add two integers and return the result as a string."""
+    return str(a + b)