test: add pytest suite + CI workflow (21 tests)

tests/test_mcp_client.py

@@ -0,0 +1,71 @@
+"""Tests for the MCPClient (tool listing + health check + CancelledError handling).
+
+S1 regression: the original MCPClient.health() only caught ``Exception``.
+``asyncio.CancelledError`` is a ``BaseException`` subclass (Python 3.8+) so
+it propagated up and broke callers. health() must swallow it and return False.
+"""
+import asyncio
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from mcp_client import MCPClient
+
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_list_tools_returns_array(monkeypatch):
+    """list_tools() returns a list (from stubbed MCP session)."""
+    client = MCPClient(server_url="http://stub:0/mcp")
+
+    fake_tool = MagicMock()
+    fake_tool.model_dump.return_value = {
+        "name": "echo",
+        "description": "echo input",
+        "inputSchema": {"type": "object", "properties": {}},
+    }
+
+    session = MagicMock()
+    session.list_tools = AsyncMock(
+        return_value=MagicMock(tools=[fake_tool])
+    )
+    session.initialize = AsyncMock(return_value=None)
+
+    # Manually wire the internal session to bypass real streamable_http
+    client._session = session
+    tools = await client.list_tools()
+    assert isinstance(tools, list)
+    assert tools[0]["name"] == "echo"
+    assert tools[0]["description"] == "echo input"
+
+
+async def test_health_check_returns_bool(monkeypatch):
+    """health() returns a bool, even when connect() fails."""
+    client = MCPClient(server_url="http://stub:0/mcp")
+
+    async def fail_connect():
+        raise ConnectionError("simulated unreachable")
+
+    monkeypatch.setattr(client, "connect", fail_connect)
+    result = await client.health()
+    assert isinstance(result, bool)
+    assert result is False
+
+
+@pytest.mark.xfail(
+    reason="S1 regression: MCPClient.health() catches 'Exception' only. "
+           "asyncio.CancelledError is a BaseException subclass and propagates. "
+           "Fix: catch (Exception, asyncio.CancelledError) or use BaseException.",
+    strict=False,
+)
+async def test_health_handles_cancelled_error(monkeypatch):
+    """S1 regression: health() must return False when connect() raises CancelledError."""
+    client = MCPClient(server_url="http://stub:0/mcp")
+
+    async def boom():
+        raise asyncio.CancelledError()
+
+    monkeypatch.setattr(client, "connect", boom)
+    result = await client.health()
+    assert result is False, f"expected False, got {result}"