test(mcp): add structured_content preservation tests

tests/test_mcp_structured_content.py

@@ -0,0 +1,100 @@
+"""Tests for MCP tool structured_content preservation."""
+
+import json
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+from tools import mcp_tool
+
+
+class _FakeContentBlock:
+    """Minimal content block with .text and .type attributes."""
+
+    def __init__(self, text: str, block_type: str = "text"):
+        self.text = text
+        self.type = block_type
+
+
+class _FakeCallToolResult:
+    """Minimal CallToolResult stand-in."""
+
+    def __init__(self, content, is_error=False, structured_content=None):
+        self.content = content
+        self.isError = is_error
+        self.structured_content = structured_content
+
+
+@pytest.fixture
+def _patch_mcp_server():
+    """Patch _servers and the MCP event loop so _make_tool_handler can run."""
+    fake_session = MagicMock()
+    fake_server = SimpleNamespace(session=fake_session)
+    with patch.dict(mcp_tool._servers, {"test-server": fake_server}):
+        yield fake_session
+
+
+class TestStructuredContentPreservation:
+    """Ensure structured_content from CallToolResult is forwarded."""
+
+    def test_text_only_result(self, _patch_mcp_server):
+        """When no structured_content, result is text-only (existing behaviour)."""
+        session = _patch_mcp_server
+        session.call_tool = AsyncMock(
+            return_value=_FakeCallToolResult(
+                content=[_FakeContentBlock("hello")],
+            )
+        )
+        handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
+        raw = handler({})
+        data = json.loads(raw)
+        assert data == {"result": "hello"}
+        assert "structuredContent" not in data
+
+    def test_structured_content_included(self, _patch_mcp_server):
+        """When structured_content is present, it must appear in the response."""
+        session = _patch_mcp_server
+        payload = {"value": "secret-123", "revealed": True}
+        session.call_tool = AsyncMock(
+            return_value=_FakeCallToolResult(
+                content=[_FakeContentBlock("OK")],
+                structured_content=payload,
+            )
+        )
+        handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
+        raw = handler({})
+        data = json.loads(raw)
+        assert data["result"] == "OK"
+        assert data["structuredContent"] == payload
+
+    def test_structured_content_none_omitted(self, _patch_mcp_server):
+        """When structured_content is explicitly None, key is omitted."""
+        session = _patch_mcp_server
+        session.call_tool = AsyncMock(
+            return_value=_FakeCallToolResult(
+                content=[_FakeContentBlock("done")],
+                structured_content=None,
+            )
+        )
+        handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
+        raw = handler({})
+        data = json.loads(raw)
+        assert data == {"result": "done"}
+        assert "structuredContent" not in data
+
+    def test_empty_text_with_structured_content(self, _patch_mcp_server):
+        """When content blocks are empty but structured_content exists."""
+        session = _patch_mcp_server
+        payload = {"status": "ok", "data": [1, 2, 3]}
+        session.call_tool = AsyncMock(
+            return_value=_FakeCallToolResult(
+                content=[],
+                structured_content=payload,
+            )
+        )
+        handler = mcp_tool._make_tool_handler("test-server", "my-tool", 30.0)
+        raw = handler({})
+        data = json.loads(raw)
+        assert data["result"] == ""
+        assert data["structuredContent"] == payload