test_model.py

# coding: utf-8
# 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.

"""
Tests for ``_zkapauthorizer.model``.
"""

from datetime import datetime, timedelta
from errno import EACCES
from os import mkdir
from unittest import skipIf

from fixtures import TempDir
from hypothesis import assume, given, note
from hypothesis.stateful import (
    RuleBasedStateMachine,
    invariant,
    precondition,
    rule,
    run_state_machine_as_test,
)
from hypothesis.strategies import (
    booleans,
    data,
    datetimes,
    integers,
    lists,
    randoms,
    timedeltas,
    tuples,
)
from testtools import TestCase
from testtools.matchers import (
    AfterPreprocessing,
    Always,
    Equals,
    HasLength,
    IsInstance,
    MatchesAll,
    MatchesStructure,
    Raises,
)
from testtools.twistedsupport import succeeded
from twisted.python.runtime import platform

from ..model import (
    DoubleSpend,
    LeaseMaintenanceActivity,
    NotEnoughTokens,
    Pass,
    Pending,
    Redeemed,
    StoreOpenError,
    Voucher,
    VoucherStore,
    memory_connect,
)
from .fixtures import ConfiglessMemoryVoucherStore, TemporaryVoucherStore
from .matchers import raises
from .strategies import (
    dummy_ristretto_keys,
    pass_counts,
    posix_safe_datetimes,
    random_tokens,
    tahoe_configs,
    unblinded_tokens,
    voucher_counters,
    voucher_objects,
    vouchers,
    zkaps,
)


class VoucherStoreTests(TestCase):
    """
    Tests for ``VoucherStore``.
    """

    @given(tahoe_configs(), datetimes(), vouchers())
    def test_get_missing(self, get_config, now, voucher):
        """
        ``VoucherStore.get`` raises ``KeyError`` when called with a
        voucher not previously added to the store.
        """
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        self.assertThat(
            lambda: store.get(voucher),
            raises(KeyError),
        )

    @given(
        tahoe_configs(),
        vouchers(),
        lists(random_tokens(), min_size=1, unique=True),
        datetimes(),
    )
    def test_add(self, get_config, voucher, tokens, now):
        """
        ``VoucherStore.get`` returns a ``Voucher`` representing a voucher
        previously added to the store with ``VoucherStore.add``.
        """
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        store.add(voucher, len(tokens), 0, lambda: tokens)
        self.assertThat(
            store.get(voucher),
            MatchesStructure(
                number=Equals(voucher),
                expected_tokens=Equals(len(tokens)),
                state=Equals(Pending(counter=0)),
                created=Equals(now),
            ),
        )

    @given(
        tahoe_configs(),
        vouchers(),
        lists(voucher_counters(), unique=True, min_size=2, max_size=2),
        lists(random_tokens(), min_size=2, unique=True),
        datetimes(),
    )
    def test_add_with_distinct_counters(
        self, get_config, voucher, counters, tokens, now
    ):
        """
        ``VoucherStore.add`` adds new tokens to the store when passed the same
        voucher but a different counter value.
        """
        counter_a = counters[0]
        counter_b = counters[1]
        tokens_a = tokens[: len(tokens) // 2]
        tokens_b = tokens[len(tokens) // 2 :]

        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        # We only have to get the expected_tokens value (len(tokens)) right on
        # the first call.
        added_tokens_a = store.add(voucher, len(tokens), counter_a, lambda: tokens_a)
        added_tokens_b = store.add(voucher, 0, counter_b, lambda: tokens_b)

        self.assertThat(
            store.get(voucher),
            MatchesStructure(
                number=Equals(voucher),
                expected_tokens=Equals(len(tokens)),
                state=Equals(Pending(counter=0)),
                created=Equals(now),
            ),
        )

        self.assertThat(tokens_a, Equals(added_tokens_a))
        self.assertThat(tokens_b, Equals(added_tokens_b))

    @given(
        tahoe_configs(),
        vouchers(),
        datetimes(),
        lists(random_tokens(), min_size=1, unique=True),
    )
    def test_add_idempotent(self, get_config, voucher, now, tokens):
        """
        More than one call to ``VoucherStore.add`` with the same argument results
        in the same state as a single call.
        """
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        first_tokens = store.add(
            voucher,
            expected_tokens=len(tokens),
            counter=0,
            get_tokens=lambda: tokens,
        )
        second_tokens = store.add(
            voucher,
            # The voucher should already exists in the store so the
            # expected_tokens value supplied here is ignored.
            expected_tokens=0,
            counter=0,
            # Likewise, no need to generate tokens here because counter value
            # 0 was already added and tokens were generated then.  If
            # get_tokens were called here, it would be an error.
            get_tokens=None,
        )
        self.assertThat(
            store.get(voucher),
            MatchesStructure(
                number=Equals(voucher),
                expected_tokens=Equals(len(tokens)),
                created=Equals(now),
                state=Equals(Pending(counter=0)),
            ),
        )
        self.assertThat(
            first_tokens,
            Equals(tokens),
        )
        self.assertThat(
            second_tokens,
            Equals(tokens),
        )

    @given(tahoe_configs(), datetimes(), lists(vouchers(), unique=True), data())
    def test_list(self, get_config, now, vouchers, data):
        """
        ``VoucherStore.list`` returns a ``list`` containing a ``Voucher`` object
        for each voucher previously added.
        """
        tokens = iter(
            data.draw(
                lists(
                    random_tokens(),
                    unique=True,
                    min_size=len(vouchers),
                    max_size=len(vouchers),
                ),
            )
        )
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        for voucher in vouchers:
            store.add(
                voucher,
                expected_tokens=1,
                counter=0,
                get_tokens=lambda: [next(tokens)],
            )

        self.assertThat(
            store.list(),
            Equals(
                list(
                    Voucher(number, expected_tokens=1, created=now)
                    for number in vouchers
                )
            ),
        )

    @skipIf(platform.isWindows(), "Hard to prevent directory creation on Windows")
    @given(tahoe_configs(), datetimes())
    def test_uncreateable_store_directory(self, get_config, now):
        """
        If the underlying directory in the node configuration cannot be created
        then ``VoucherStore.from_node_config`` raises ``StoreOpenError``.
        """
        tempdir = self.useFixture(TempDir())
        nodedir = tempdir.join(u"node")

        # Create the node directory without permission to create the
        # underlying directory.
        mkdir(nodedir, 0o500)

        config = get_config(nodedir, u"tub.port")

        self.assertThat(
            lambda: VoucherStore.from_node_config(
                config,
                lambda: now,
                memory_connect,
            ),
            Raises(
                AfterPreprocessing(
                    lambda exc_info: exc_info[1],
                    MatchesAll(
                        IsInstance(StoreOpenError),
                        MatchesStructure(
                            reason=MatchesAll(
                                IsInstance(OSError),
                                MatchesStructure(
                                    errno=Equals(EACCES),
                                ),
                            ),
                        ),
                    ),
                ),
            ),
        )

    @skipIf(
        platform.isWindows(), "Hard to prevent database from being opened on Windows"
    )
    @given(tahoe_configs(), datetimes())
    def test_unopenable_store(self, get_config, now):
        """
        If the underlying database file cannot be opened then
        ``VoucherStore.from_node_config`` raises ``StoreOpenError``.
        """
        tempdir = self.useFixture(TempDir())
        nodedir = tempdir.join(u"node")

        config = get_config(nodedir, u"tub.port")

        # Create the underlying database file.
        store = VoucherStore.from_node_config(config, lambda: now)

        # Prevent further access to it.
        store.database_path.chmod(0o000)

        self.assertThat(
            lambda: VoucherStore.from_node_config(
                config,
                lambda: now,
            ),
            raises(StoreOpenError),
        )

    @given(tahoe_configs(), vouchers(), dummy_ristretto_keys(), datetimes(), data())
    def test_spend_order_equals_backup_order(
        self, get_config, voucher_value, public_key, now, data
    ):
        """
        Unblinded tokens returned by ``VoucherStore.backup`` appear in the same
        order as they are returned by ``VoucherStore.get_unblinded_tokens``.
        """
        backed_up_tokens, spent_tokens, inserted_tokens = self._spend_order_test(
            get_config, voucher_value, public_key, now, data
        )
        self.assertThat(
            backed_up_tokens,
            Equals(spent_tokens),
        )

    @given(tahoe_configs(), vouchers(), dummy_ristretto_keys(), datetimes(), data())
    def test_spend_order_equals_insert_order(
        self, get_config, voucher_value, public_key, now, data
    ):
        """
        Unblinded tokens returned by ``VoucherStore.get_unblinded_tokens``
        appear in the same order as they were inserted.
        """
        backed_up_tokens, spent_tokens, inserted_tokens = self._spend_order_test(
            get_config, voucher_value, public_key, now, data
        )
        self.assertThat(
            spent_tokens,
            Equals(inserted_tokens),
        )

    def _spend_order_test(self, get_config, voucher_value, public_key, now, data):
        """
        Insert, backup, and extract some tokens.

        :param get_config: See ``tahoe_configs``
        :param unicode voucher_value: A voucher value to associate with the tokens.
        :param unicode public_key: A public key to associate with inserted unblinded tokens.
        :param datetime now: A time to pretend is current.
        :param data: A Hypothesis data for drawing values from strategies.

        :return: A three-tuple of (backed up tokens, extracted tokens, inserted tokens).
        """
        tempdir = self.useFixture(TempDir())
        nodedir = tempdir.join(u"node")

        config = get_config(nodedir, u"tub.port")

        # Create the underlying database file.
        store = VoucherStore.from_node_config(config, lambda: now)

        # Put some tokens in it that we can backup and extract
        random_tokens, unblinded_tokens = paired_tokens(
            data, integers(min_value=1, max_value=5)
        )
        store.add(voucher_value, len(random_tokens), 0, lambda: random_tokens)
        store.insert_unblinded_tokens_for_voucher(
            voucher_value,
            public_key,
            unblinded_tokens,
            completed=data.draw(booleans()),
            spendable=True,
        )

        backed_up_tokens = store.backup()[u"unblinded-tokens"]
        extracted_tokens = []
        tokens_remaining = len(unblinded_tokens)
        while tokens_remaining > 0:
            to_spend = data.draw(integers(min_value=1, max_value=tokens_remaining))
            extracted_tokens.extend(
                token.unblinded_token.decode("ascii")
                for token in store.get_unblinded_tokens(to_spend)
            )
            tokens_remaining -= to_spend

        return (
            backed_up_tokens,
            extracted_tokens,
            list(token.unblinded_token.decode("ascii") for token in unblinded_tokens),
        )


class UnblindedTokenStateMachine(RuleBasedStateMachine):
    """
    Transition rules for a state machine corresponding to the state of
    unblinded tokens in a ``VoucherStore`` - usable, in-use, spent, invalid,
    etc.
    """

    def __init__(self, case):
        super(UnblindedTokenStateMachine, self).__init__()
        self.case = case
        self.configless = ConfiglessMemoryVoucherStore(
            # Time probably not actually relevant to this state machine.
            datetime.now,
        )
        self.configless.setUp()

        self.available = 0
        self.using = []
        self.spent = []
        self.invalid = []

    def teardown(self):
        self.configless.cleanUp()

    @rule(voucher=vouchers(), num_passes=pass_counts())
    def redeem_voucher(self, voucher, num_passes):
        """
        A voucher can be redeemed, adding more unblinded tokens to the store.
        """
        try:
            self.configless.store.get(voucher)
        except KeyError:
            pass
        else:
            # Cannot redeem a voucher more than once.  We redeemed this one
            # already.
            assume(False)

        self.case.assertThat(
            self.configless.redeem(voucher, num_passes),
            succeeded(Always()),
        )
        self.available += num_passes

    @rule(num_passes=pass_counts())
    def get_passes(self, num_passes):
        """
        Some passes can be requested from the store.  The resulting passes are not
        spent, invalid, or already in-use.
        """
        assume(num_passes <= self.available)
        tokens = self.configless.store.get_unblinded_tokens(num_passes)
        note("get_passes: {}".format(tokens))

        # No tokens we are currently using may be returned again.  Nor may
        # tokens which have reached a terminal state of spent or invalid.
        unavailable = set(self.using) | set(self.spent) | set(self.invalid)

        self.case.assertThat(
            tokens,
            MatchesAll(
                HasLength(num_passes),
                AfterPreprocessing(
                    lambda t: set(t) & unavailable,
                    Equals(set()),
                ),
            ),
        )
        self.using.extend(tokens)
        self.available -= num_passes

    @rule(excess_passes=pass_counts())
    def not_enough_passes(self, excess_passes):
        """
        If an attempt is made to get more passes than are available,
        ``get_unblinded_tokens`` raises ``NotEnoughTokens``.
        """
        self.case.assertThat(
            lambda: self.configless.store.get_unblinded_tokens(
                self.available + excess_passes,
            ),
            raises(NotEnoughTokens),
        )

    @precondition(lambda self: len(self.using) > 0)
    @rule(random=randoms(), data=data())
    def spend_passes(self, random, data):
        """
        Some in-use passes can be discarded.
        """
        self.using, to_spend = random_slice(self.using, random, data)
        note("spend_passes: {}".format(to_spend))
        self.configless.store.discard_unblinded_tokens(to_spend)

    @precondition(lambda self: len(self.using) > 0)
    @rule(random=randoms(), data=data())
    def reset_passes(self, random, data):
        """
        Some in-use passes can be returned to not-in-use state.
        """
        self.using, to_reset = random_slice(self.using, random, data)
        note("reset_passes: {}".format(to_reset))
        self.configless.store.reset_unblinded_tokens(to_reset)
        self.available += len(to_reset)

    @precondition(lambda self: len(self.using) > 0)
    @rule(random=randoms(), data=data())
    def invalidate_passes(self, random, data):
        """
        Some in-use passes are unusable and should be set aside.
        """
        self.using, to_invalidate = random_slice(self.using, random, data)
        note("invalidate_passes: {}".format(to_invalidate))
        self.configless.store.invalidate_unblinded_tokens(
            u"reason",
            to_invalidate,
        )
        self.invalid.extend(to_invalidate)

    @rule()
    def discard_ephemeral_state(self):
        """
        Reset all state that cannot outlive a single process, simulating a
        restart.

        XXX We have to reach into the guts of ``VoucherStore`` to do this
        because we're using an in-memory database.  We can't just open a new
        ``VoucherStore``. :/ Perhaps we should use an on-disk database...  Or
        maybe this is a good argument for using an explicitly attached
        temporary database instead of the built-in ``temp`` database.
        """
        with self.configless.store._connection:
            self.configless.store._connection.execute(
                """
                DELETE FROM [in-use]
                """,
            )
        self.available += len(self.using)
        del self.using[:]

    @invariant()
    def report_state(self):
        note(
            "available={} using={} invalid={} spent={}".format(
                self.available,
                len(self.using),
                len(self.invalid),
                len(self.spent),
            )
        )


def random_slice(taken_from, random, data):
    """
    Divide ``taken_from`` into two pieces with elements randomly assigned to
    one piece or the other.

    :param list taken_from: A list of elements to divide.  This will be
        mutated.

    :param random: A ``random`` module-alike.

    :param data: A Hypothesis data object for drawing values.

    :return: A two-tuple of the two resulting lists.
    """
    count = data.draw(integers(min_value=1, max_value=len(taken_from)))
    random.shuffle(taken_from)
    remaining = taken_from[:-count]
    sliced = taken_from[-count:]
    return remaining, sliced


class UnblindedTokenStateTests(TestCase):
    """
    Glue ``UnblindedTokenStateTests`` into our test runner.
    """

    def test_states(self):
        run_state_machine_as_test(lambda: UnblindedTokenStateMachine(self))


class LeaseMaintenanceTests(TestCase):
    """
    Tests for the lease-maintenance related parts of ``VoucherStore``.
    """

    @given(
        tahoe_configs(),
        posix_safe_datetimes(),
        lists(
            tuples(
                # How much time passes before this activity starts
                timedeltas(min_value=timedelta(1), max_value=timedelta(days=1)),
                # Some activity.  This list of two tuples gives us a trivial
                # way to compute the total passes required (just sum the pass
                # counts in it).  This is nice because it avoids having the
                # test re-implement size quantization which would just be
                # repeated code duplicating the implementation.  The second
                # value lets us fuzz the actual size values a little bit in a
                # way which shouldn't affect the passes required.
                lists(
                    tuples(
                        # The activity itself, in pass count
                        integers(min_value=1, max_value=2 ** 16 - 1),
                        # Amount by which to trim back the share sizes.  This
                        # might exceed the value of a single pass but we don't
                        # know that value yet.  We'll map it into a coherent
                        # range with mod inside the test.
                        integers(min_value=0),
                    ),
                ),
                # How much time passes before this activity finishes
                timedeltas(min_value=timedelta(1), max_value=timedelta(days=1)),
            ),
        ),
    )
    def test_lease_maintenance_activity(self, get_config, now, activity):
        """
        ``VoucherStore.get_latest_lease_maintenance_activity`` returns a
        ``LeaseMaintenanceTests`` with fields reflecting the most recently
        finished lease maintenance activity.
        """
        store = self.useFixture(
            TemporaryVoucherStore(get_config, lambda: now),
        ).store

        expected = None
        for (start_delay, sizes, finish_delay) in activity:
            now += start_delay
            started = now
            x = store.start_lease_maintenance()
            passes_required = 0
            for (num_passes, trim_size) in sizes:
                passes_required += num_passes
                trim_size %= store.pass_value
                x.observe(
                    [
                        num_passes * store.pass_value - trim_size,
                    ]
                )
            now += finish_delay
            x.finish()
            finished = now

            # Let the last iteration of the loop define the expected value.
            expected = LeaseMaintenanceActivity(
                started,
                passes_required,
                finished,
            )

        self.assertThat(
            store.get_latest_lease_maintenance_activity(),
            Equals(expected),
        )


class VoucherTests(TestCase):
    """
    Tests for ``Voucher``.
    """

    @given(voucher_objects())
    def test_json_roundtrip(self, reference):
        """
        ``Voucher.to_json . Voucher.from_json → id``
        """
        self.assertThat(
            Voucher.from_json(reference.to_json()),
            Equals(reference),
        )


def paired_tokens(data, sizes=integers(min_value=1, max_value=1000)):
    """
    Draw two lists of the same length, one of random tokens and one of
    unblinded tokens.

    :rtype: ([RandomTokens], [UnblindedTokens])
    """
    num_tokens = data.draw(sizes)
    r = data.draw(
        lists(
            random_tokens(),
            min_size=num_tokens,
            max_size=num_tokens,
            unique=True,
        )
    )
    u = data.draw(
        lists(
            unblinded_tokens(),
            min_size=num_tokens,
            max_size=num_tokens,
            unique=True,
        )
    )
    return r, u


class UnblindedTokenStoreTests(TestCase):
    """
    Tests for ``UnblindedToken``-related functionality of ``VoucherStore``.
    """

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
        dummy_ristretto_keys(),
        lists(unblinded_tokens(), unique=True),
        booleans(),
    )
    def test_unblinded_tokens_without_voucher(
        self, get_config, now, voucher_value, public_key, unblinded_tokens, completed
    ):
        """
        Unblinded tokens for a voucher which has not been added to the store cannot be inserted.
        """
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        self.assertThat(
            lambda: store.insert_unblinded_tokens_for_voucher(
                voucher_value,
                public_key,
                unblinded_tokens,
                completed,
                spendable=True,
            ),
            raises(ValueError),
        )

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
        dummy_ristretto_keys(),
        booleans(),
        data(),
    )
    def test_unblinded_tokens_round_trip(
        self, get_config, now, voucher_value, public_key, completed, data
    ):
        """
        Unblinded tokens that are added to the store can later be retrieved and counted.
        """
        random_tokens, unblinded_tokens = paired_tokens(data)
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        store.add(voucher_value, len(random_tokens), 0, lambda: random_tokens)
        store.insert_unblinded_tokens_for_voucher(
            voucher_value, public_key, unblinded_tokens, completed, spendable=True
        )

        # All the tokens just inserted should be counted.
        self.expectThat(
            store.count_unblinded_tokens(),
            Equals(len(unblinded_tokens)),
        )
        retrieved_tokens = store.get_unblinded_tokens(len(random_tokens))

        # All the tokens just extracted should not be counted.
        self.expectThat(
            store.count_unblinded_tokens(),
            Equals(0),
        )

        self.expectThat(
            set(unblinded_tokens),
            Equals(set(retrieved_tokens)),
        )

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
        dummy_ristretto_keys(),
        integers(min_value=1, max_value=100),
        data(),
    )
    def test_mark_vouchers_redeemed(
        self, get_config, now, voucher_value, public_key, num_tokens, data
    ):
        """
        The voucher for unblinded tokens that are added to the store is marked as
        redeemed.
        """
        random = data.draw(
            lists(
                random_tokens(),
                min_size=num_tokens,
                max_size=num_tokens,
                unique=True,
            ),
        )
        unblinded = data.draw(
            lists(
                unblinded_tokens(),
                min_size=num_tokens,
                max_size=num_tokens,
                unique=True,
            ),
        )

        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        store.add(voucher_value, len(random), 0, lambda: random)
        store.insert_unblinded_tokens_for_voucher(
            voucher_value, public_key, unblinded, completed=True, spendable=True
        )
        loaded_voucher = store.get(voucher_value)
        self.assertThat(
            loaded_voucher,
            MatchesStructure(
                expected_tokens=Equals(len(random)),
                state=Equals(
                    Redeemed(
                        finished=now,
                        token_count=num_tokens,
                    )
                ),
            ),
        )

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
        lists(random_tokens(), min_size=1, unique=True),
    )
    def test_mark_vouchers_double_spent(
        self, get_config, now, voucher_value, random_tokens
    ):
        """
        A voucher which is reported as double-spent is marked in the database as
        such.
        """
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        store.add(voucher_value, len(random_tokens), 0, lambda: random_tokens)
        store.mark_voucher_double_spent(voucher_value)
        voucher = store.get(voucher_value)
        self.assertThat(
            voucher,
            MatchesStructure(
                state=Equals(
                    DoubleSpend(
                        finished=now,
                    )
                ),
            ),
        )

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
        dummy_ristretto_keys(),
        integers(min_value=1, max_value=100),
        data(),
    )
    def test_mark_spent_vouchers_double_spent(
        self, get_config, now, voucher_value, public_key, num_tokens, data
    ):
        """
        A voucher which has already been spent cannot be marked as double-spent.
        """
        random = data.draw(
            lists(
                random_tokens(),
                min_size=num_tokens,
                max_size=num_tokens,
                unique=True,
            ),
        )
        unblinded = data.draw(
            lists(
                unblinded_tokens(),
                min_size=num_tokens,
                max_size=num_tokens,
                unique=True,
            ),
        )
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        store.add(voucher_value, len(random), 0, lambda: random)
        store.insert_unblinded_tokens_for_voucher(
            voucher_value, public_key, unblinded, completed=True, spendable=True
        )
        self.assertThat(
            lambda: store.mark_voucher_double_spent(voucher_value),
            raises(ValueError),
        )

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
    )
    def test_mark_invalid_vouchers_double_spent(self, get_config, now, voucher_value):
        """
        A voucher which is not known cannot be marked as double-spent.
        """
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        self.assertThat(
            lambda: store.mark_voucher_double_spent(voucher_value),
            raises(ValueError),
        )

    @given(
        tahoe_configs(),
        datetimes(),
        vouchers(),
        dummy_ristretto_keys(),
        booleans(),
        integers(min_value=1),
        data(),
    )
    def test_not_enough_unblinded_tokens(
        self, get_config, now, voucher_value, public_key, completed, extra, data
    ):
        """
        ``get_unblinded_tokens`` raises ``NotEnoughTokens`` if ``count`` is
        greater than the number of unblinded tokens in the store.
        """
        random, unblinded = paired_tokens(data)
        num_tokens = len(random)
        store = self.useFixture(TemporaryVoucherStore(get_config, lambda: now)).store
        store.add(voucher_value, len(random), 0, lambda: random)
        store.insert_unblinded_tokens_for_voucher(
            voucher_value,
            public_key,
            unblinded,
            completed,
            spendable=True,
        )
        self.assertThat(
            lambda: store.get_unblinded_tokens(num_tokens + extra),
            raises(NotEnoughTokens),
        )


def store_for_test(testcase, get_config, get_now):
    """
    Create a ``VoucherStore`` in a temporary directory associated with the
    given test case.

    :param TestCase testcase: The test case for which to build the store.
    :param get_config: A function like the one built by ``tahoe_configs``.
    :param get_now: A no-argument callable that returns a datetime giving a
        time to consider as "now".

    :return VoucherStore: A newly created temporary store.
    """
    tempdir = testcase.useFixture(TempDir())
    config = get_config(tempdir.join(u"node"), u"tub.port")
    store = VoucherStore.from_node_config(
        config,
        get_now,
        memory_connect,
    )
    return store


class PassTests(TestCase):
    """
    Tests for ``Pass``.
    """

    @given(zkaps())
    def test_roundtrip(self, pass_):
        """
        ``Pass`` round-trips through ``Pass.from_bytes`` and ``Pass.pass_bytes``.
        """
        self.assertThat(
            Pass.from_bytes(pass_.pass_bytes),
            Equals(pass_),
        )