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/agents/test_flash_runner.py

@@ -0,0 +1,113 @@
+# 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.
+
+"""Unit tests for Universal FlashRunner."""
+
+from unittest.mock import Mock, patch
+import pytest
+from langchain_core.messages import HumanMessage, ToolMessage
+
+from artemis.agents.flash.runner import FlashRunner
+from artemis.context import ArtemisContext
+
+
+@pytest.fixture
+def mock_context():
+    ctx = Mock(spec=ArtemisContext)
+    ctx.llm_config = Mock()
+    mock_llm_cfg = Mock()
+    mock_llm_cfg.model = "gemini-2.5-flash"
+    mock_llm_cfg.temperature = 0.1
+    ctx.llm_config.get_agent.return_value = mock_llm_cfg
+
+    ctx.device = Mock()
+    ctx.device.device_width = 1080
+    ctx.device.device_height = 2400
+    ctx.data_engine = None
+    ctx.adb_client = None
+    ctx.driver = Mock()
+    return ctx
+
+
+def test_flash_runner_tools_initialization(mock_context):
+    """Verify FlashRunner gathers correct active tools."""
+    with patch("artemis.controllers.unified_controller.get_driver"):
+        runner = FlashRunner(mock_context, goal="Test Open Settings")
+        tools = runner._get_tools()
+
+        tool_names = [t.name for t in tools]
+        assert "click" in tool_names
+        assert "click_sequence" in tool_names
+        assert "swipe" in tool_names
+        assert "input_text" in tool_names
+        assert "ask_explorer" in tool_names
+        assert "report_task_status" in tool_names
+        # Validator's report_failure_analysis should NOT be in FlashRunner
+        assert "report_failure_analysis" not in tool_names
+
+
+def test_flash_runner_screenshot_pruning(mock_context):
+    """Verify that earlier screenshot blocks are pruned, keeping only the latest."""
+    with patch("artemis.controllers.unified_controller.get_driver"):
+        runner = FlashRunner(mock_context, goal="Test Pruning")
+
+        messages = [
+            HumanMessage(
+                content=[
+                    {"type": "text", "text": "Turn 1 goal"},
+                    {
+                        "type": "image_url",
+                        "image_url": {"url": "data:image/jpeg;base64,SCREENSHOT_1"},
+                    },
+                ]
+            ),
+            ToolMessage(
+                tool_call_id="tc1",
+                name="click",
+                content=[
+                    {"type": "text", "text": "Clicked button"},
+                    {
+                        "type": "image_url",
+                        "image_url": {"url": "data:image/jpeg;base64,SCREENSHOT_2"},
+                    },
+                ],
+            ),
+            ToolMessage(
+                tool_call_id="tc2",
+                name="swipe",
+                content=[
+                    {"type": "text", "text": "Swiped up"},
+                    {
+                        "type": "image_url",
+                        "image_url": {"url": "data:image/jpeg;base64,SCREENSHOT_3"},
+                    },
+                ],
+            ),
+        ]
+
+        runner._prune_intermediate_screenshots(messages)
+
+        # Check Turn 1: image should be removed
+        assert len(messages[0].content) == 1
+        assert messages[0].content[0]["type"] == "text"
+
+        # Check Turn 2 (Tool 1): image should be removed
+        assert len(messages[1].content) == 1
+        assert messages[1].content[0]["type"] == "text"
+
+        # Check Turn 3 (Tool 2 - Latest): image MUST be preserved
+        assert len(messages[2].content) == 2
+        assert messages[2].content[0]["type"] == "text"
+        assert messages[2].content[1]["type"] == "image_url"
+        assert messages[2].content[1]["image_url"]["url"] == "data:image/jpeg;base64,SCREENSHOT_3"