python-tdd/src/core/runner.py

import pickle
import time
from django.test.runner import DiscoverRunner, ParallelTestSuite, RemoteTestRunner


class _Py313SafeRemoteTestRunner(RemoteTestRunner):
    """Prevents Python 3.13 'cannot pickle traceback' crash in parallel workers.

    In Python 3.13, traceback objects are not picklable. Django's parallel
    runner tries to pickle test errors to pass them back to the main process.
    When a Selenium test crashes the browser, the resulting exception traceback
    fails to pickle, aborting the entire parallel run with a confusing TypeError.

    Fix: strip the traceback (replace with None) before it reaches pickle.
    Error type and message are preserved; only the traceback is lost in transit.
    """

    @staticmethod
    def _strip_tb_if_needed(err):
        exc_type, exc_value, exc_tb = err
        try:
            pickle.dumps((exc_type, exc_value, exc_tb))
        except (TypeError, AttributeError):
            return (exc_type, exc_value, None)
        return err

    def addError(self, test, err):
        super().addError(test, self._strip_tb_if_needed(err))

    def addFailure(self, test, err):
        super().addFailure(test, self._strip_tb_if_needed(err))


class _SafeParallelTestSuite(ParallelTestSuite):
    runner_class = _Py313SafeRemoteTestRunner


class RobustCompressorTestRunner(DiscoverRunner):
    parallel_test_suite = _SafeParallelTestSuite

    def setup_test_environment(self, **kwargs):
        super().setup_test_environment(**kwargs)
        from compressor.storage import CompressorFileStorage
        _orig_save = CompressorFileStorage.save
        def _robust_save(self, name, content):
            for _ in range(5):
                try: return _orig_save(self, name, content)
                except PermissionError: time.sleep(0.05)
            raise
        CompressorFileStorage.save = _robust_save