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_update_note_pure_tool.py

@@ -0,0 +1,146 @@
+# 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 MagicMock, patch
+
+from artemis.context import ArtemisContext
+from artemis.tools.base import ArtemisTool, ToolRegistry
+from artemis.tools.scratchpad import (
+    UpdateNoteArgs,
+    UpdateNotePure,
+    UpdateNotePureTool,
+    get_update_note_tool_pure,
+    update_note_pure,
+)
+from artemis.utils.notes import save_note_content
+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_update_note_pure_tool_subclass_and_registry():
+    """Verify UpdateNotePureTool is a subclass of ArtemisTool and properly registered."""
+    assert issubclass(UpdateNotePureTool, ArtemisTool)
+    assert issubclass(UpdateNotePure, ArtemisTool)
+    assert isinstance(update_note_pure, ArtemisTool)
+    assert isinstance(update_note_pure, UpdateNotePureTool)
+
+    assert update_note_pure.name == "update_note_pure"
+    assert update_note_pure.category == "memory"
+    assert update_note_pure.args_schema == UpdateNoteArgs
+
+    # Registry lookup
+    reg_tool = ToolRegistry.get("update_note_pure")
+    assert reg_tool is not None
+    assert isinstance(reg_tool, UpdateNotePureTool)
+
+    # GenAI FunctionDeclaration export
+    declaration = update_note_pure.to_genai_declaration()
+    assert declaration.name == "update_note_pure"
+    assert "key" in declaration.parameters.properties
+    assert "target" in declaration.parameters.properties
+    assert "replacement" in declaration.parameters.properties
+
+
+@pytest.mark.asyncio
+async def test_update_note_pure_direct_execution_success(mock_ctx, tmp_path):
+    """Verify direct execution of UpdateNotePureTool.execute updates existing note."""
+    save_note_content(tmp_path, "plan", "Step 1: Pending\nStep 2: Done")
+
+    result = await update_note_pure.execute(
+        ctx=mock_ctx,
+        key="plan",
+        target="Step 1: Pending",
+        replacement="Step 1: Completed",
+    )
+    assert result == "Successfully updated note 'plan'."
+
+    note_path = Path(tmp_path) / "notes" / "plan.md"
+    assert note_path.read_text(encoding="utf-8") == "Step 1: Completed\nStep 2: Done"
+
+
+@pytest.mark.asyncio
+async def test_update_note_pure_with_warning(mock_ctx, tmp_path):
+    """Verify update note pure handles warning from fuzzy matching."""
+    save_note_content(tmp_path, "fuzzy_note", "Target String")
+
+    with patch(
+        "artemis.tools.scratchpad.update_note_content",
+        return_value="Fuzzy match applied",
+    ):
+        result = await update_note_pure.execute(
+            ctx=mock_ctx,
+            key="fuzzy_note",
+            target="target string",
+            replacement="New String",
+        )
+        assert "Successfully updated note 'fuzzy_note'." in result
+        assert "WARNING: Fuzzy match applied" in result
+
+
+@pytest.mark.asyncio
+async def test_update_note_pure_callable_execution(mock_ctx, tmp_path):
+    """Verify invoking update_note_pure directly as a callable."""
+    save_note_content(tmp_path, "callable_plan", "alpha beta")
+
+    result = await update_note_pure(
+        ctx=mock_ctx,
+        key="callable_plan",
+        target="beta",
+        replacement="gamma",
+    )
+    assert result == "Successfully updated note 'callable_plan'."
+
+    note_path = Path(tmp_path) / "notes" / "callable_plan.md"
+    assert note_path.read_text(encoding="utf-8") == "alpha gamma"
+
+
+@pytest.mark.asyncio
+async def test_update_note_pure_execution_failure(mock_ctx):
+    """Verify error handling when note update fails."""
+    result = await update_note_pure.execute(
+        ctx=mock_ctx,
+        key="missing_note",
+        target="old",
+        replacement="new",
+    )
+    assert "Failed to update note 'missing_note':" in result
+
+
+@pytest.mark.asyncio
+async def test_get_update_note_tool_pure_langchain_ainvoke(mock_ctx, tmp_path):
+    """Verify get_update_note_tool_pure exports a LangChain tool named 'update_note'."""
+    save_note_content(tmp_path, "export_plan", "initial value")
+
+    pure_tool = get_update_note_tool_pure(mock_ctx)
+    assert pure_tool.name == "update_note"
+
+    result = await pure_tool.ainvoke(
+        {
+            "key": "export_plan",
+            "target": "initial",
+            "replacement": "updated",
+        }
+    )
+    assert result == "Successfully updated note 'export_plan'."
+
+    note_path = Path(tmp_path) / "notes" / "export_plan.md"
+    assert note_path.read_text(encoding="utf-8") == "updated value"