Source code for hypothesis.extra.dpcontracts

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"""
-----------------------
hypothesis[dpcontracts]
-----------------------

This module provides tools for working with the :pypi:`dpcontracts` library,
because `combining contracts and property-based testing works really well
<https://hillelwayne.com/talks/beyond-unit-tests/>`_.

It requires ``dpcontracts >= 0.4``.
"""

from __future__ import absolute_import, division, print_function

from dpcontracts import PreconditionError

from hypothesis import reject
from hypothesis.errors import InvalidArgument
from hypothesis.internal.reflection import proxies


[docs]def fulfill(contract_func): """Decorate ``contract_func`` to reject calls which violate preconditions, and retry them with different arguments. This is a convenience function for testing internal code that uses :pypi:dpcontracts`, to automatically filter out arguments that would be rejected by the public interface before triggering a contract error. This can be used as ``builds(fulfill(func), ...)`` or in the body of the test e.g. ``assert fulfill(func)(*args)``. """ if not hasattr(contract_func, "__contract_wrapped_func__"): raise InvalidArgument( "There are no dpcontracts preconditions associated with %s" % (contract_func.__name__,) ) @proxies(contract_func) def inner(*args, **kwargs): try: return contract_func(*args, **kwargs) except PreconditionError: reject() return inner