try:

            self.CacheFile = kwargs.pop('file_class')

        except KeyError:

            pass

class WriteCacheFile(CacheFileBase):

    ERRORS_MAP = []

class CacheWriter(CacheBase):

    CacheFile = WriteCacheFile

    def open(self, path):

        return self.CacheFile(path, 'w')

    CacheFile = ReadCacheFile

        return self.CacheFile(path)

import datetime

import io

import pathlib

import pytest

from . import any_date, relpath

import oxrlib.cache

import oxrlib.errors

CACHE_PATH = relpath('writecache')

HISTORICAL_PATTERN = '{date}_{base}_cache.json'

class TestCacheFile(oxrlib.cache.WriteCacheFile):

    def __init__(self, path, *args, **kwargs):

        self.path = path

        assert args[0].startswith('w')

    def open(self):

        open_file = io.StringIO()

        open_file.name = self.path.as_posix()

        return open_file

@pytest.fixture

def dummycache():

    cache = oxrlib.cache.CacheWriter(CACHE_PATH, file_class=TestCacheFile)

    cache.setup(historical=HISTORICAL_PATTERN)

    return cache

def test_cache_success(dummycache, any_date):

    base = 'USD'

    expect_name = CACHE_PATH / HISTORICAL_PATTERN.format(date=any_date.isoformat(), base=base)

    with dummycache.historical(any_date, base) as cache_file:

        assert pathlib.Path(cache_file.name) == expect_name