[Misc] Cleanup: use consistent pytest-mock in unit tests (#2698)

Signed-off-by: yuanheng <jonathan.zhaoyh@gmail.com>

tests/engine/test_async_omni_engine_outputs.py

@@ -5,36 +5,36 @@ subsequent attempts to collect output raise RuntimeError.
 """
 
 import queue
-from unittest.mock import MagicMock
 
 import pytest
+from pytest_mock import MockerFixture
 
 from vllm_omni.engine.async_omni_engine import AsyncOmniEngine
 
 pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
 
 
-def _make_engine(output_queue, *, thread_alive: bool = True) -> AsyncOmniEngine:
+def _make_engine(output_queue, mocker: MockerFixture, *, thread_alive: bool = True) -> AsyncOmniEngine:
     """Create an AsyncOmniEngine bypassing __init__."""
     engine = object.__new__(AsyncOmniEngine)
     engine.output_queue = output_queue
-    engine.orchestrator_thread = MagicMock(
-        is_alive=MagicMock(return_value=thread_alive),
+    engine.orchestrator_thread = mocker.MagicMock(
+        is_alive=mocker.MagicMock(return_value=thread_alive),
     )
     return engine
 
 
-def test_try_get_output_raises_after_orchestrator_dies():
+def test_try_get_output_raises_after_orchestrator_dies(mocker: MockerFixture):
     """Draining remaining results then hitting an empty queue with a dead
     orchestrator must raise RuntimeError so callers know the pipeline is gone."""
-    mock_queue = MagicMock()
+    mock_queue = mocker.MagicMock()
     # First call succeeds; second call finds the queue empty.
     mock_queue.sync_q.get.side_effect = [
         {"type": "output", "request_id": "r1"},
         queue.Empty,
     ]
 
-    engine = _make_engine(mock_queue, thread_alive=True)
+    engine = _make_engine(mock_queue, mocker, thread_alive=True)
 
     # Collect the one buffered result.
     assert engine.try_get_output()["request_id"] == "r1"
@@ -47,15 +47,15 @@ def test_try_get_output_raises_after_orchestrator_dies():
 
 
 @pytest.mark.asyncio
-async def test_try_get_output_async_raises_after_orchestrator_dies():
+async def test_try_get_output_async_raises_after_orchestrator_dies(mocker: MockerFixture):
     """Same scenario as above but for the async variant."""
-    mock_queue = MagicMock()
+    mock_queue = mocker.MagicMock()
     mock_queue.sync_q.get_nowait.side_effect = [
         {"type": "output", "request_id": "r1"},
         queue.Empty,
     ]
 
-    engine = _make_engine(mock_queue, thread_alive=True)
+    engine = _make_engine(mock_queue, mocker, thread_alive=True)
 
     assert (await engine.try_get_output_async())["request_id"] == "r1"