test: add comprehensive unit, integration, and e2e test suites

Introduce complete test coverage for the ARTEMIS platform across multiple layers:
Unit tests: Add tests for agent nodes (Planner, Operator, Validator, Diagnoser, FlashRunner, Explorer), tools, utils (OCR/XML fusion, UI hierarchy), and data engine.
Integration tests: Add live tool verification, reactive runner, IME, and standalone workflow tests.
E2E tests: Add end-to-end scenario tests for media playback and failure recovery flows.
Fixtures & mocks: Add mock inputs (audio, video, screenshot) and test utilities.

tests/unit/tools/test_list_notes_tool.py

@@ -0,0 +1,158 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from unittest.mock import AsyncMock, MagicMock, patch
+
+from artemis.constants import VALIDATOR_MESSAGES_KEY
+from artemis.context import ArtemisContext
+from artemis.graph.state import State
+from artemis.tools.base import ArtemisTool, ToolRegistry
+from artemis.tools.scratchpad import (
+    ListNotes,
+    ListNotesArgs,
+    ListNotesTool,
+    get_list_notes_tool,
+    get_list_notes_tool_pure,
+    list_notes,
+    list_notes_wrapper,
+)
+from artemis.utils.notes import save_note_content
+from langgraph.types import Command
+import pytest
+
+
+@pytest.fixture
+def mock_ctx(tmp_path):
+    ctx = MagicMock(spec=ArtemisContext)
+    ctx.data_engine = MagicMock()
+    ctx.data_engine.base_dir = str(tmp_path)
+    return ctx
+
+
+def test_list_notes_tool_subclass_and_registry():
+    """Verify ListNotesTool is a subclass of ArtemisTool and properly registered."""
+    assert issubclass(ListNotesTool, ArtemisTool)
+    assert issubclass(ListNotes, ArtemisTool)
+    assert isinstance(list_notes, ArtemisTool)
+    assert isinstance(list_notes, ListNotesTool)
+
+    assert list_notes.name == "list_notes"
+    assert list_notes.category == "memory"
+    assert list_notes.args_schema == ListNotesArgs
+
+    # Registry lookup
+    reg_tool = ToolRegistry.get("list_notes")
+    assert reg_tool is not None
+    assert isinstance(reg_tool, ListNotesTool)
+
+    # GenAI FunctionDeclaration export
+    declaration = list_notes.to_genai_declaration()
+    assert declaration.name == "list_notes"
+
+    # Wrapper check
+    assert list_notes_wrapper is not None
+    assert list_notes_wrapper.tool_fn_getter == get_list_notes_tool
+
+
+@pytest.mark.asyncio
+async def test_list_notes_direct_execution_empty(mock_ctx):
+    """Verify listing notes when no notes are stored."""
+    result = await list_notes.execute(ctx=mock_ctx)
+    assert "No notes saved yet." in result
+
+
+@pytest.mark.asyncio
+async def test_list_notes_direct_execution_success(mock_ctx, tmp_path):
+    """Verify direct execution of ListNotesTool.execute lists stored notes."""
+    save_note_content(tmp_path, "note_alpha", "line 1\nline 2")
+    save_note_content(tmp_path, "note_beta", "single line")
+
+    result = await list_notes.execute(ctx=mock_ctx)
+    assert "Here are all the notes:" in result
+    assert "- note_alpha (2 lines)" in result
+    assert "- note_beta (1 lines)" in result
+
+
+@pytest.mark.asyncio
+async def test_list_notes_callable_execution(mock_ctx, tmp_path):
+    """Verify invoking list_notes directly as a callable."""
+    save_note_content(tmp_path, "note_gamma", "line A\nline B\nline C")
+
+    result = await list_notes(ctx=mock_ctx)
+    assert "Here are all the notes:" in result
+    assert "- note_gamma (3 lines)" in result
+
+
+@pytest.mark.asyncio
+async def test_list_notes_with_state_command(mock_ctx, tmp_path):
+    """Verify ListNotesTool.execute with state returns Command updating VALIDATOR_MESSAGES_KEY."""
+    save_note_content(tmp_path, "state_note", "content")
+
+    mock_state = MagicMock(spec=State)
+    mock_state.current_agent = "operator"
+    mock_state.asanitize_update = AsyncMock(side_effect=lambda ctx, update, agent: update)
+
+    result = await list_notes.execute(
+        ctx=mock_ctx,
+        state=mock_state,
+        tool_call_id="call_list_999",
+    )
+
+    assert isinstance(result, Command)
+    assert VALIDATOR_MESSAGES_KEY in result.update
+    tool_messages = result.update[VALIDATOR_MESSAGES_KEY]
+    assert len(tool_messages) == 1
+    assert tool_messages[0].tool_call_id == "call_list_999"
+    assert "Here are all the notes:" in tool_messages[0].content
+    assert "- state_note (1 lines)" in tool_messages[0].content
+    assert tool_messages[0].status == "success"
+
+    mock_state.asanitize_update.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_list_notes_execution_failure(mock_ctx):
+    """Verify error handling when list_notes fails."""
+    with patch(
+        "artemis.tools.scratchpad.list_notes_info",
+        side_effect=RuntimeError("Disk failure"),
+    ):
+        result = await list_notes.execute(ctx=mock_ctx)
+        assert "Failed to list notes: Disk failure" in result
+
+
+@pytest.mark.asyncio
+async def test_get_list_notes_tool_langchain_ainvoke(mock_ctx, tmp_path):
+    """Verify get_list_notes_tool exports a LangChain tool that works with ainvoke."""
+    save_note_content(tmp_path, "lc_note", "hello")
+
+    lc_tool = get_list_notes_tool(mock_ctx)
+    assert lc_tool.name == "list_notes"
+
+    result = await lc_tool.ainvoke({})
+    assert "Here are all the notes:" in result
+    assert "- lc_note (1 lines)" in result
+
+
+@pytest.mark.asyncio
+async def test_get_list_notes_tool_pure(mock_ctx, tmp_path):
+    """Verify get_list_notes_tool_pure returns a pure LangChain tool."""
+    save_note_content(tmp_path, "pure_note", "world")
+
+    pure_tool = get_list_notes_tool_pure(mock_ctx)
+    assert pure_tool.name == "list_notes"
+
+    result = await pure_tool.ainvoke({})
+    assert "Here are all the notes:" in result
+    assert "- pure_note (1 lines)" in result