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-rw-r--r--cloudinit/tests/test_persistence.py127
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diff --git a/cloudinit/tests/test_persistence.py b/cloudinit/tests/test_persistence.py
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-# Copyright (C) 2020 Canonical Ltd.
-#
-# Author: Daniel Watkins <oddbloke@ubuntu.com>
-#
-# This file is part of cloud-init. See LICENSE file for license information.
-"""
-Tests for cloudinit.persistence.
-
-Per https://docs.python.org/3/library/pickle.html, only "classes that are
-defined at the top level of a module" can be pickled. This means that all of
-our ``CloudInitPickleMixin`` subclasses for testing must be defined at
-module-level (rather than being defined inline or dynamically in the body of
-test methods, as we would do without this constraint).
-
-``TestPickleMixin.test_subclasses`` iterates over a list of all of these
-classes, and tests that they round-trip through a pickle dump/load. As the
-interface we're testing is that ``_unpickle`` is called appropriately on
-subclasses, our subclasses define their assertions in their ``_unpickle``
-implementation. (This means that the assertions will not be executed if
-``_unpickle`` is not called at all; we have
-``TestPickleMixin.test_unpickle_called`` to ensure it is called.)
-
-To avoid manually maintaining a list of classes for parametrization we use a
-simple metaclass, ``_Collector``, to gather them up.
-"""
-
-import pickle
-from unittest import mock
-
-import pytest
-
-from cloudinit.persistence import CloudInitPickleMixin
-
-
-class _Collector(type):
- """Any class using this as a metaclass will be stored in test_classes."""
-
- test_classes = []
-
- def __new__(cls, *args):
- new_cls = super().__new__(cls, *args)
- _Collector.test_classes.append(new_cls)
- return new_cls
-
-
-class InstanceVersionNotUsed(CloudInitPickleMixin, metaclass=_Collector):
- """Test that the class version is used over one set in instance state."""
-
- _ci_pkl_version = 1
-
- def __init__(self):
- self._ci_pkl_version = 2
-
- def _unpickle(self, ci_pkl_version: int) -> None:
- assert 1 == ci_pkl_version
-
-
-class MissingVersionHandled(CloudInitPickleMixin, metaclass=_Collector):
- """Test that pickles without ``_ci_pkl_version`` are handled gracefully.
-
- This is tested by overriding ``__getstate__`` so the dumped pickle of this
- class will not have ``_ci_pkl_version`` included.
- """
-
- def __getstate__(self):
- return self.__dict__
-
- def _unpickle(self, ci_pkl_version: int) -> None:
- assert 0 == ci_pkl_version
-
-
-class OverridenVersionHonored(CloudInitPickleMixin, metaclass=_Collector):
- """Test that the subclass's version is used."""
-
- _ci_pkl_version = 1
-
- def _unpickle(self, ci_pkl_version: int) -> None:
- assert 1 == ci_pkl_version
-
-
-class StateIsRestored(CloudInitPickleMixin, metaclass=_Collector):
- """Instance state should be restored before ``_unpickle`` is called."""
-
- def __init__(self):
- self.some_state = "some state"
-
- def _unpickle(self, ci_pkl_version: int) -> None:
- assert "some state" == self.some_state
-
-
-class UnpickleCanBeUnoverriden(CloudInitPickleMixin, metaclass=_Collector):
- """Subclasses should not need to override ``_unpickle``."""
-
-
-class VersionDefaultsToZero(CloudInitPickleMixin, metaclass=_Collector):
- """Test that the default version is 0."""
-
- def _unpickle(self, ci_pkl_version: int) -> None:
- assert 0 == ci_pkl_version
-
-
-class VersionIsPoppedFromState(CloudInitPickleMixin, metaclass=_Collector):
- """Test _ci_pkl_version is popped from state before being restored."""
-
- def _unpickle(self, ci_pkl_version: int) -> None:
- # `self._ci_pkl_version` returns the type's _ci_pkl_version if it isn't
- # in instance state, so we need to explicitly check self.__dict__.
- assert "_ci_pkl_version" not in self.__dict__
-
-
-class TestPickleMixin:
- def test_unpickle_called(self):
- """Test that self._unpickle is called on unpickle."""
- with mock.patch.object(
- CloudInitPickleMixin, "_unpickle"
- ) as m_unpickle:
- pickle.loads(pickle.dumps(CloudInitPickleMixin()))
- assert 1 == m_unpickle.call_count
-
- @pytest.mark.parametrize("cls", _Collector.test_classes)
- def test_subclasses(self, cls):
- """For each collected class, round-trip through pickle dump/load.
-
- Assertions are implemented in ``cls._unpickle``, and so are evoked as
- part of the pickle load.
- """
- pickle.loads(pickle.dumps(cls()))