matchers.py

# Copyright 2019 PrivateStorage.io, LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Testtools matchers useful for the test suite.
"""

__all__ = [
    "Provides",
    "raises",
    "returns",
    "matches_version_dictionary",
    "between",
    "leases_current",
]

from datetime import (
    datetime,
)

import attr

from testtools.matchers import (
    Matcher,
    Mismatch,
    ContainsDict,
    Always,
    MatchesAll,
    MatchesAny,
    GreaterThan,
    LessThan,
    Equals,
    AfterPreprocessing,
    AllMatch,
)

from ._exception import (
    raises,
)

@attr.s
class Provides(object):
    """
    Match objects that provide all of a list of Zope Interface interfaces.
    """
    interfaces = attr.ib()

    def match(self, obj):
        missing = set()
        for iface in self.interfaces:
            if not iface.providedBy(obj):
                missing.add(iface)
        if missing:
            return Mismatch("{} does not provide expected {}".format(
                obj, ", ".join(str(iface) for iface in missing),
            ))


def matches_version_dictionary():
    """
    Match the dictionary returned by Tahoe-LAFS'
    ``RIStorageServer.get_version`` which is also the dictionary returned by
    our own ``RIPrivacyPassAuthorizedStorageServer.get_version``.
    """
    return ContainsDict({
        # It has these two top-level keys, at least.  Try not to be too
        # fragile by asserting much more than that they are present.
        b'application-version': Always(),
        b'http://allmydata.org/tahoe/protocols/storage/v1': Always(),
    })



def returns(matcher):
    """
    Matches a no-argument callable that returns a value matched by the given
    matcher.
    """
    return _Returns(matcher)



class _Returns(Matcher):
    def __init__(self, result_matcher):
        self.result_matcher = result_matcher


    def match(self, matchee):
        return self.result_matcher.match(matchee())


    def __str__(self):
        return "Returns({})".format(self.result_matcher)


def greater_or_equal(v):
    """
    Matches a value greater than or equal to ``v``.
    """
    return MatchesAny(GreaterThan(v), Equals(v))


def lesser_or_equal(v):
    """
    Matches a value less than or equal to ``v``.
    """
    return MatchesAny(LessThan(v), Equals(v))


def between(low, high):
    """
    Matches a value in the range [low, high].
    """
    return MatchesAll(
        greater_or_equal(low),
        lesser_or_equal(high),
    )


def leases_current(relevant_storage_indexes, now, min_lease_remaining):
    """
    Return a matcher on a ``DummyStorageServer`` instance which matches
    servers for which the leases on the given storage indexes do not expire
    before ``min_lease_remaining``.
    """
    return AfterPreprocessing(
        # Get share stats for storage indexes we should have
        # visited and maintained.
        lambda storage_server: list(
            stat
            for (storage_index, stat)
            in storage_server.buckets.items()
            if storage_index in relevant_storage_indexes
        ),
        AllMatch(
            AfterPreprocessing(
                # Lease expiration for anything visited must be
                # further in the future than min_lease_remaining,
                # either because it had time left or because we
                # renewed it.
                lambda share_stat: datetime.utcfromtimestamp(share_stat.lease_expiration),
                GreaterThan(now + min_lease_remaining),
            ),
        ),
    )