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/tools/conftest.py

@@ -0,0 +1,95 @@
+# 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
+
+from artemis.context import ArtemisContext
+from artemis.data_engine.engine import DataEngine
+import pytest
+
+INPUTS_DIR = Path(__file__).parent / "inputs"
+
+
+@pytest.fixture(scope="session")
+def inputs_dir():
+    return INPUTS_DIR
+
+
+@pytest.fixture
+def mock_adb_client():
+    client = MagicMock()
+    # Dummy outputs for commands and physical interactions that tools might use
+    client.shell.return_value = "dummy adb output"
+    # Basic UI hierarchy for mobile read_hierarchy tool
+    client.get_hierarchy.return_value = (
+        "<?xml version='1.0' encoding='UTF-8'?><hierarchy><node index='0'"
+        " text='dummy'/></hierarchy>"
+    )
+    return client
+
+
+@pytest.fixture
+def artemis_context(inputs_dir, mock_adb_client):
+    """Provides a ArtemisContext with loaded database and actual side-effects,
+
+    except the ADB connection is customized to read from fixtures instead of a
+    real device.
+    """
+    ctx = MagicMock(spec=ArtemisContext)
+
+    ctx.execution_setup = MagicMock()
+    ctx.execution_setup.traces_path = str(inputs_dir)
+
+    # Initialize real DataEngine if the fixture database exists
+    db_path = inputs_dir / "data_engine.db"
+    if db_path.exists():
+        engine = DataEngine(ctx)
+        engine.start_session(goal="Test goal")
+        import uuid
+
+        engine.current_step_id = uuid.uuid4()
+        ctx.data_engine = engine
+    else:
+        ctx.data_engine = None
+
+    ctx.ui_adb_client = mock_adb_client
+
+    # Fake device representation
+    ctx.device = MagicMock()
+    ctx.device.device_width = 1080
+    ctx.device.device_height = 2400
+
+    # Trace output directory setup to point inside inputs or a dedicated test folder
+    trace_out = inputs_dir / "trace_output"
+    trace_out.mkdir(exist_ok=True)
+    ctx.trace_dir = trace_out
+
+    ctx.agent_config = MagicMock()
+    ctx.agent_config.blacklisted_tools = {}
+
+    return ctx
+
+
+@pytest.fixture
+def mock_state(inputs_dir):
+    """Provides a dummy graph State with realistic artifact paths for tools that need state injection."""
+    from artemis.graph.state import State
+
+    state = MagicMock(spec=State)
+    state.latest_screenshot = str(inputs_dir / "screenshot.jpg")
+    state.video_path = str(inputs_dir / "recording.mp4")
+    state.indexed_points = []
+    state.indexed_elements = []
+    return state