import warnings from typing import Union, Type from testfixtures import Comparison as C, compare WarningOrType = Union[Warning, Type[Warning]] class ShouldWarn(warnings.catch_warnings): """ This context manager is used to assert that warnings are issued within the context it is managing. :param expected: This should be a sequence made up of one or more elements, each of one of the following types: * A warning class, indicating that the type of the warnings is important but not the parameters it is created with. * A warning instance, indicating that a warning exactly matching the one supplied should have been issued. If no expected warnings are passed, you will need to inspect the contents of the list returned by the context manager. :param filters: If passed, these are used to create a filter such that only warnings you are interested in will be considered by this :class:`ShouldWarn` instance. The names and meanings are the same as the parameters for :func:`warnings.filterwarnings`. """ _empty_okay = False def __init__(self, *expected: WarningOrType, **filters): super(ShouldWarn, self).__init__(record=True) self.expected = [C(e) for e in expected] self.filters = filters def __enter__(self): self.recorded = super(ShouldWarn, self).__enter__() warnings.filterwarnings("always", **self.filters) return self.recorded def __exit__(self, exc_type, exc_val, exc_tb): super(ShouldWarn, self).__exit__(exc_type, exc_val, exc_tb) if not self.recorded and self._empty_okay: return if not self.expected and self.recorded and not self._empty_okay: return compare(self.expected, actual=[wm.message for wm in self.recorded]) class ShouldNotWarn(ShouldWarn): """ This context manager is used to assert that no warnings are issued within the context it is managing. """ _empty_okay = True def __init__(self): super(ShouldNotWarn, self).__init__()