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/image_processor/test_image_processor_tools.py

@@ -0,0 +1,43 @@
+# 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 artemis.tools.image_processor_tool import get_ask_image_processor_tool
+import pytest
+
+
+@pytest.mark.asyncio
+async def test_ask_image_processor_tool(artemis_context, mock_state):
+    """Tests the ask_image_processor tool as a blackbox.
+
+    Allows actual side effects and full lifecycle execution (including real LLM
+    API calls). Uses shared pytest fixtures for realistic context.
+    """
+    tool = get_ask_image_processor_tool(artemis_context)
+
+    # Passing a simple visual reasoning instruction.
+    # The tool will use target_image_id="img_0" corresponding to the artifact in mock_state.
+    result = await tool.ainvoke(
+        {
+            "instruction": "Identify the primary colors present in this image.",
+            "target_image_id": "img_0",
+            "state": mock_state,
+        }
+    )
+
+    # Assert execution without errors and produces expected output structure
+    assert result is not None
+    assert isinstance(result, dict)
+    assert "outputs" in result
+    assert "summary" in result
+    assert isinstance(result["outputs"], list)