AttributeError: 'NoneType' object has no attribute 'start'

[mmerlo]

I'm seeing an issue with pytest-qt (4.4.0) and I am not sure if it is a thread issue on my end or an issue with pytest-qt. Most of the time, the test will pass, but this issue will cause the test to fail about 10% to 20% of the time. Below is code that reproduces the issue:

from PySide6.QtCore import QThread, QObject, Signal
import traceback

class MyRelay(QObject):
    sig_to_relay = Signal()

class MyWorker(QObject):
    my_signal = Signal()

    def __init__(self, relay):
        super().__init__()
        self._relay = relay
        self._relay.setParent(self)
        self._relay.sig_to_relay.connect(self.my_signal)

    
class MyThread(QObject):
    def __init__(self):
        self._workers = None
        self._thread = QThread()

    def add_worker(self, worker):
        self._workers  = worker

    def start(self):
        self._workers.moveToThread(self._thread)
        self._thread.start()


class TestThread:
    def test_error_1(self, qtbot):
        relay = MyRelay()
        mw = MyWorker(relay)
        my_thread = MyThread()
        my_thread.add_worker(mw)
        my_thread.start()

        try:
            with qtbot.waitSignal(
                mw.my_signal, timeout=500) as blocker:
                relay.sig_to_relay.emit()
                print(blocker)
        except Exception as e:
            traceback.print_exc()
            raise e
        my_thread._thread.quit()
        my_thread._thread.wait()

In this example, the try block is to catch the exception before it fails the test so that I can check the traceback. During failures, the traceback is:

Traceback (most recent call last):
  File "~python_work/pytest_qt_qthread/test_pytest_qt.py", line 41, in test_warning_message
    with qtbot.waitSignal(
  File "~python_work/pytest_qt_qthread/.venv/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 151, in __exit__
    self.wait()
  File "~python_work/pytest_qt_qthread/.venv/lib/python3.12/site-packages/pytestqt/wait_signal.py", line 48, in wait
    self._timer.start()
    ^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'start'

It appears that the a timer in pytest-qt is getting through the timer is None check but then is None when self._timer.start() is called a few lines later.

Also, on every run of the test (in debug mode), the following message is reported QObject::killTimer: Timers cannot be stopped from another thread, which may be related.

Any idea on what may be wrong here?

Thanks.