testutils.py

import pytest
from _pytest.python_api import ApproxBase
from _pytest.assertion.util import _compare_eq_dict


# Subclassing ApproxBase means we can patch into the pytest machinery for
# custom assertion error messages, since that class provides a `_repr_compare` method
# that is not present on any other types.
# https://github.com/pytest-dev/pytest/blob/556e075d23a91eb42821129a5d874ec3174e17ad/src/_pytest/assertion/util.py#L219
# There doesn't appear to be any other API to do this.
class ContainsSubdict(ApproxBase):
    """
    Tests True for equality against a superdict that contains a subdict
    """

    def __init__(self, subdict):
        self.subdict = subdict

    def __repr__(self):
        return repr(self.subdict)

    def _repr_compare(self, superdict):
        if isinstance(self.subdict, list):
            for i, subdict, superdict in enumerate(
                zip_longest(self.subdict, superdict)
            ):
                if not subdict.items() <= superdict.items():
                    return [
                        "comparison failed at item {i} of list:",
                        *self._repr_compare_dicts(subdict, superdict),
                    ]
            return []
        else:
            return self._repr_compare_dicts(self.subdict, superdict)

    def _repr_compare_dicts(self, subdict, superdict):
        # Just return the error message for dict equality, but first subtract the items that are
        # not relevant to the subdict, otherwise the error message will be too noisy.
        smaller_superdict = {k: v for (k, v) in superdict.items() if k in subdict}
        return _compare_eq_dict(smaller_superdict, subdict)

    def __eq__(self, superdict):
        if isinstance(self.subdict, list):
            for subdict, superdict in zip_longest(self.subdict, superdict):
                if not subdict.items() <= superdict.items():
                    return False
        else:
            if not self.subdict.items() <= superdict.items():
                return False

        return True