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_save_note_tool.py

@@ -0,0 +1,180 @@
+# 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 pathlib import Path
+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 (
+    SaveNote,
+    SaveNoteArgs,
+    SaveNoteTool,
+    get_save_note_tool,
+    get_save_note_tool_pure,
+    save_note,
+    save_note_wrapper,
+)
+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_save_note_tool_subclass_and_registry():
+    """Verify SaveNoteTool is a subclass of ArtemisTool and properly registered in ToolRegistry."""
+    assert issubclass(SaveNoteTool, ArtemisTool)
+    assert issubclass(SaveNote, ArtemisTool)
+    assert isinstance(save_note, ArtemisTool)
+    assert isinstance(save_note, SaveNoteTool)
+
+    assert save_note.name == "save_note"
+    assert save_note.category == "memory"
+    assert save_note.args_schema == SaveNoteArgs
+
+    # Registry lookup
+    reg_tool = ToolRegistry.get("save_note")
+    assert reg_tool is not None
+    assert isinstance(reg_tool, SaveNoteTool)
+
+    # GenAI FunctionDeclaration export
+    declaration = save_note.to_genai_declaration()
+    assert declaration.name == "save_note"
+    assert "key" in declaration.parameters.properties
+    assert "content" in declaration.parameters.properties
+
+    # Wrapper check
+    assert save_note_wrapper is not None
+    assert save_note_wrapper.tool_fn_getter == get_save_note_tool
+
+
+@pytest.mark.asyncio
+async def test_save_note_direct_execution_success(mock_ctx, tmp_path):
+    """Verify direct execution of SaveNoteTool.execute creates note file."""
+    result = await save_note.execute(
+        ctx=mock_ctx,
+        key="test_note",
+        content="Hello Artemis memory",
+    )
+    assert result == "Successfully saved note to test_note.md."
+
+    note_path = Path(tmp_path) / "notes" / "test_note.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Hello Artemis memory"
+
+
+@pytest.mark.asyncio
+async def test_save_note_callable_execution(mock_ctx, tmp_path):
+    """Verify invoking save_note directly as a callable."""
+    result = await save_note(
+        ctx=mock_ctx,
+        key="callable_note",
+        content="Callable invocation test",
+    )
+    assert result == "Successfully saved note to callable_note.md."
+
+    note_path = Path(tmp_path) / "notes" / "callable_note.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Callable invocation test"
+
+
+@pytest.mark.asyncio
+async def test_save_note_with_state_command(mock_ctx, tmp_path):
+    """Verify SaveNoteTool.execute with state returns Command updating VALIDATOR_MESSAGES_KEY."""
+    mock_state = MagicMock(spec=State)
+    mock_state.current_agent = "operator"
+    mock_state.asanitize_update = AsyncMock(side_effect=lambda ctx, update, agent: update)
+
+    result = await save_note.execute(
+        ctx=mock_ctx,
+        key="state_note",
+        content="Note with state",
+        state=mock_state,
+        tool_call_id="call_save_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_save_999"
+    assert tool_messages[0].content == "Successfully saved note to state_note.md."
+    assert tool_messages[0].status == "success"
+
+    mock_state.asanitize_update.assert_called_once()
+
+    note_path = Path(tmp_path) / "notes" / "state_note.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Note with state"
+
+
+@pytest.mark.asyncio
+async def test_save_note_execution_failure(mock_ctx):
+    """Verify error handling when saving note fails."""
+    with patch(
+        "artemis.tools.scratchpad.save_note_content",
+        side_effect=PermissionError("Permission denied"),
+    ):
+        result = await save_note.execute(
+            ctx=mock_ctx,
+            key="fail_note",
+            content="Fail content",
+        )
+        assert "Failed to save note fail_note.md: Permission denied" in result
+
+
+@pytest.mark.asyncio
+async def test_get_save_note_tool_langchain_ainvoke(mock_ctx, tmp_path):
+    """Verify get_save_note_tool exports a LangChain tool that works with ainvoke."""
+    lc_tool = get_save_note_tool(mock_ctx)
+    assert lc_tool.name == "save_note"
+
+    result = await lc_tool.ainvoke(
+        {
+            "key": "lc_note",
+            "content": "Saved via LangChain BaseTool",
+        }
+    )
+    assert result == "Successfully saved note to lc_note.md."
+
+    note_path = Path(tmp_path) / "notes" / "lc_note.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Saved via LangChain BaseTool"
+
+
+@pytest.mark.asyncio
+async def test_get_save_note_tool_pure(mock_ctx, tmp_path):
+    """Verify get_save_note_tool_pure returns a pure LangChain tool."""
+    pure_tool = get_save_note_tool_pure(mock_ctx)
+    assert pure_tool.name == "save_note"
+
+    result = await pure_tool.ainvoke(
+        {
+            "key": "pure_note",
+            "content": "Saved via pure tool",
+        }
+    )
+    assert result == "Successfully saved note to pure_note.md."
+
+    note_path = Path(tmp_path) / "notes" / "pure_note.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Saved via pure tool"