Stabilize task execution and UI lifecycle

tests/unit/runtime/test_device_lock.py

@@ -0,0 +1,110 @@
+# 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.
+
+import json
+
+import pytest
+
+from artemis.runtime.device_lock import DeviceBusyError, DeviceExecutionLock
+
+
+@pytest.fixture(autouse=True)
+def isolated_lock_directory(tmp_path, monkeypatch):
+    monkeypatch.setattr(
+        "artemis.runtime.device_lock.get_temp_dir",
+        lambda _name: tmp_path,
+    )
+
+
+def test_device_lock_blocks_a_second_process_owner():
+    first = DeviceExecutionLock("emulator-5554", "first task")
+    second = DeviceExecutionLock("emulator-5554", "second task")
+
+    first.acquire()
+    try:
+        with pytest.raises(DeviceBusyError, match="first task"):
+            second.acquire()
+    finally:
+        first.release()
+
+
+def test_device_lock_recovers_stale_owner(monkeypatch):
+    lock = DeviceExecutionLock("emulator-5554", "replacement task")
+    lock.path.write_text(
+        json.dumps(
+            {
+                "pid": 999999,
+                "process_created_at": 1.0,
+                "token": "stale-token",
+                "device_id": "emulator-5554",
+                "description": "stale task",
+                "acquired_at": "2026-01-01T00:00:00+00:00",
+            }
+        ),
+        encoding="utf-8",
+    )
+    monkeypatch.setattr(DeviceExecutionLock, "_owner_is_alive", staticmethod(lambda _owner: False))
+
+    lock.acquire()
+    try:
+        assert lock.path.exists()
+    finally:
+        lock.release()
+
+    assert not lock.path.exists()
+
+
+def test_device_lock_release_does_not_remove_replacement_owner():
+    lock = DeviceExecutionLock("emulator-5554", "original task")
+    lock.acquire()
+    replacement = json.loads(lock.path.read_text(encoding="utf-8"))
+    replacement["token"] = "replacement-token"
+    lock.path.write_text(json.dumps(replacement), encoding="utf-8")
+
+    lock.release()
+
+    assert lock.path.exists()
+
+
+def test_cleanup_stale_locks_keeps_live_owner(monkeypatch):
+    live = DeviceExecutionLock("emulator-5554", "live task")
+    stale = DeviceExecutionLock("physical-device", "stale task")
+    live.acquire()
+    stale.path.write_text(
+        json.dumps(
+            {
+                "pid": 999999,
+                "process_created_at": 1.0,
+                "token": "stale-token",
+                "device_id": "physical-device",
+                "description": "stale task",
+                "acquired_at": "2026-01-01T00:00:00+00:00",
+            }
+        ),
+        encoding="utf-8",
+    )
+    original_owner_is_alive = DeviceExecutionLock._owner_is_alive
+
+    def owner_is_alive(owner):
+        if owner.pid == 999999:
+            return False
+        return original_owner_is_alive(owner)
+
+    monkeypatch.setattr(DeviceExecutionLock, "_owner_is_alive", staticmethod(owner_is_alive))
+    try:
+        assert DeviceExecutionLock.cleanup_stale_locks() == 1
+        assert live.path.exists()
+        assert not stale.path.exists()
+    finally:
+        live.release()