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_read_hierarchy_tool.py

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+# 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
+
+from artemis.context import ArtemisContext
+from artemis.drivers.base import BaseDeviceDriver
+from artemis.tools.base import ArtemisTool, ToolRegistry
+from artemis.tools.mobile.read_hierarchy import (
+    GetUIHierarchy,
+    GetUiHierarchy,
+    GetUiHierarchyArgs,
+    GetUiHierarchyTool,
+    get_ui_hierarchy,
+    get_ui_hierarchy_tool,
+    ui_hierarchy_wrapper,
+)
+import pytest
+
+
+@pytest.fixture
+def mock_ctx():
+    ctx = MagicMock(spec=ArtemisContext)
+    ctx.ui_adb_client = MagicMock()
+    ctx.ui_adb_client.get_hierarchy.return_value = "<hierarchy><node text='Home'/></hierarchy>"
+    return ctx
+
+
+@pytest.fixture
+def mock_driver():
+    driver = MagicMock(spec=BaseDeviceDriver)
+    screen_data = MagicMock()
+    screen_data.ui_hierarchy_xml = "<hierarchy><node text='Settings'/></hierarchy>"
+    driver.get_screen_data = AsyncMock(return_value=screen_data)
+    return driver
+
+
+def test_get_ui_hierarchy_tool_subclass_and_registry():
+    """Verify GetUiHierarchyTool is a subclass of ArtemisTool and properly registered."""
+    assert issubclass(GetUiHierarchyTool, ArtemisTool)
+    assert issubclass(GetUiHierarchy, ArtemisTool)
+    assert issubclass(GetUIHierarchy, ArtemisTool)
+    assert isinstance(get_ui_hierarchy, ArtemisTool)
+    assert isinstance(get_ui_hierarchy, GetUiHierarchyTool)
+
+    assert get_ui_hierarchy.name == "get_ui_hierarchy"
+    assert get_ui_hierarchy.category == "diagnostic"
+    assert get_ui_hierarchy.args_schema == GetUiHierarchyArgs
+
+    # Registry lookup
+    reg_tool = ToolRegistry.get("get_ui_hierarchy")
+    assert reg_tool is not None
+    assert isinstance(reg_tool, GetUiHierarchyTool)
+
+    # GenAI FunctionDeclaration export
+    declaration = get_ui_hierarchy.to_genai_declaration()
+    assert declaration.name == "get_ui_hierarchy"
+
+    # Wrapper check
+    assert ui_hierarchy_wrapper is not None
+    assert ui_hierarchy_wrapper.tool_fn_getter == get_ui_hierarchy_tool
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_direct_execution_with_ctx(mock_ctx):
+    """Verify direct execution with ArtemisContext."""
+    result = await get_ui_hierarchy.execute(ctx=mock_ctx)
+    mock_ctx.ui_adb_client.get_hierarchy.assert_called_once()
+    assert "<hierarchy><node text='Home'/></hierarchy>" in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_direct_execution_with_driver_screen_data(mock_driver):
+    """Verify direct execution with driver's get_screen_data."""
+    result = await get_ui_hierarchy.execute(driver=mock_driver)
+    mock_driver.get_screen_data.assert_called_once()
+    assert "<hierarchy><node text='Settings'/></hierarchy>" in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_direct_execution_with_driver_get_hierarchy():
+    """Verify direct execution with driver's get_ui_hierarchy."""
+    driver = MagicMock(spec=BaseDeviceDriver)
+    del driver.get_screen_data
+    driver.get_ui_hierarchy = AsyncMock(
+        return_value="<hierarchy><node text='DirectDriver'/></hierarchy>"
+    )
+    result = await get_ui_hierarchy.execute(driver=driver)
+    driver.get_ui_hierarchy.assert_called_once()
+    assert "<hierarchy><node text='DirectDriver'/></hierarchy>" in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_with_state(mock_ctx):
+    """Verify GetUiHierarchyTool returns string when state is provided."""
+    state = MagicMock()
+    result = await get_ui_hierarchy.execute(
+        ctx=mock_ctx,
+        tool_call_id="call_hier_1",
+        state=state,
+    )
+    assert "<hierarchy><node text='Home'/></hierarchy>" in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_no_client_or_driver():
+    """Verify error handling when no client or driver is provided."""
+    result = await get_ui_hierarchy.execute()
+    assert "Error retrieving UI hierarchy: No UI Automator client or driver provided." in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_exception_handling(mock_ctx):
+    """Verify error handling when ui_adb_client raises an exception."""
+    mock_ctx.ui_adb_client.get_hierarchy.side_effect = RuntimeError("ADB server died")
+    result = await get_ui_hierarchy.execute(ctx=mock_ctx)
+    assert "Error retrieving UI hierarchy: ADB server died" in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_callable_execution(mock_ctx):
+    """Verify invoking get_ui_hierarchy directly as a callable."""
+    result = await get_ui_hierarchy(ctx=mock_ctx)
+    assert "<node text='Home'/>" in result
+
+
+@pytest.mark.asyncio
+async def test_get_ui_hierarchy_tool_langchain_ainvoke(mock_ctx):
+    """Verify get_ui_hierarchy_tool exports a LangChain tool that works with ainvoke."""
+    tool = get_ui_hierarchy_tool(mock_ctx)
+    assert tool.name == "get_ui_hierarchy"
+
+    result = await tool.ainvoke({})
+    assert "<node text='Home'/>" in result