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_pure_tool.py

@@ -0,0 +1,122 @@
+# 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 (
+    SaveNoteArgs,
+    SaveNotePure,
+    SaveNotePureTool,
+    get_save_note_tool_pure,
+    save_note_pure,
+)
+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_pure_tool_subclass_and_registry():
+    """Verify SaveNotePureTool is a subclass of ArtemisTool and properly registered."""
+    assert issubclass(SaveNotePureTool, ArtemisTool)
+    assert issubclass(SaveNotePure, ArtemisTool)
+    assert isinstance(save_note_pure, ArtemisTool)
+    assert isinstance(save_note_pure, SaveNotePureTool)
+
+    assert save_note_pure.name == "save_note_pure"
+    assert save_note_pure.category == "memory"
+    assert save_note_pure.args_schema == SaveNoteArgs
+
+    # Registry lookup
+    reg_tool = ToolRegistry.get("save_note_pure")
+    assert reg_tool is not None
+    assert isinstance(reg_tool, SaveNotePureTool)
+
+    # GenAI FunctionDeclaration export
+    declaration = save_note_pure.to_genai_declaration()
+    assert declaration.name == "save_note_pure"
+    assert "key" in declaration.parameters.properties
+    assert "content" in declaration.parameters.properties
+
+
+@pytest.mark.asyncio
+async def test_save_note_pure_direct_execution_success(mock_ctx, tmp_path):
+    """Verify direct execution of SaveNotePureTool.execute creates note file."""
+    result = await save_note_pure.execute(
+        ctx=mock_ctx,
+        key="test_pure_save",
+        content="Pure saved content",
+    )
+    assert result == "Successfully saved note to test_pure_save.md."
+
+    note_path = Path(tmp_path) / "notes" / "test_pure_save.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Pure saved content"
+
+
+@pytest.mark.asyncio
+async def test_save_note_pure_callable_execution(mock_ctx, tmp_path):
+    """Verify invoking save_note_pure directly as a callable."""
+    result = await save_note_pure(
+        ctx=mock_ctx,
+        key="callable_pure_save",
+        content="Callable pure content",
+    )
+    assert result == "Successfully saved note to callable_pure_save.md."
+
+    note_path = Path(tmp_path) / "notes" / "callable_pure_save.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Callable pure content"
+
+
+@pytest.mark.asyncio
+async def test_save_note_pure_execution_failure(mock_ctx):
+    """Verify error handling when save_note_content fails."""
+    with patch(
+        "artemis.tools.scratchpad.save_note_content",
+        side_effect=PermissionError("Permission denied"),
+    ):
+        result = await save_note_pure.execute(
+            ctx=mock_ctx,
+            key="fail_save",
+            content="Some content",
+        )
+        assert "Failed to save note fail_save.md: Permission denied" in result
+
+
+@pytest.mark.asyncio
+async def test_get_save_note_tool_pure_langchain_ainvoke(mock_ctx, tmp_path):
+    """Verify get_save_note_tool_pure exports a LangChain tool named 'save_note'."""
+    pure_tool = get_save_note_tool_pure(mock_ctx)
+    assert pure_tool.name == "save_note"
+
+    result = await pure_tool.ainvoke(
+        {
+            "key": "lc_pure_save",
+            "content": "Saved via LangChain pure tool",
+        }
+    )
+    assert result == "Successfully saved note to lc_pure_save.md."
+
+    note_path = Path(tmp_path) / "notes" / "lc_pure_save.md"
+    assert note_path.exists()
+    assert note_path.read_text(encoding="utf-8") == "Saved via LangChain pure tool"