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/test_sdk.py

@@ -0,0 +1,66 @@
+# 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 the official Python SDK (ArtemisClient, Task, TaskResult)."""
+
+import pytest
+from artemis import ArtemisClient, Task, TaskResult
+
+
+@pytest.mark.asyncio
+async def test_artemis_client_run_mock():
+    """Verify ArtemisClient runs a task through the execution pipeline."""
+    client = ArtemisClient(device_id="mock-test-dev", default_profile="pro")
+    assert client.device_id == "mock-test-dev"
+    assert client.default_profile == "pro"
+
+    result = await client.run(goal="Open Settings and enable Dark Theme")
+    assert isinstance(result, TaskResult)
+    assert result.status in ("completed", "running", "success")
+    assert result.trace_id.startswith("trace_") or len(result.trace_id) > 0
+
+
+def test_task_model_validation():
+    """Verify Task validation and default arguments."""
+    task = Task(goal="Search for flight prices", profile="flash", device_id="emulator-5554")
+    assert task.goal == "Search for flight prices"
+    assert task.profile == "flash"
+    assert task.device_id == "emulator-5554"
+    assert task.max_turns == 30
+    assert task.locked_package is None
+
+
+@pytest.mark.asyncio
+async def test_artemis_client_stream_run():
+    """Verify ArtemisClient.stream_run yields real-time StreamEvents."""
+    from artemis import StreamEvent, StreamEventType
+
+    client = ArtemisClient(device_id="mock-stream-dev", default_profile="flash")
+    collected_events: list[StreamEvent] = []
+
+    def on_event(ev: StreamEvent):
+        collected_events.append(ev)
+
+    events: list[StreamEvent] = []
+    async for event in client.stream_run(
+        goal="Test streaming UI action flow",
+        profile="flash",
+        callbacks=[on_event],
+    ):
+        events.append(event)
+
+    assert len(events) >= 2
+    assert events[0].event_type == StreamEventType.STATUS
+    assert events[0].payload.get("status") == "starting"
+    assert len(collected_events) == len(events)