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fail2ban/testcases/filtertestcase.py

687 lines
23 KiB

# emacs: -*- mode: python; py-indent-offset: 4; indent-tabs-mode: t -*-
# vi: set ft=python sts=4 ts=4 sw=4 noet :
# This file is part of Fail2Ban.
#
# Fail2Ban is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# Fail2Ban is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Fail2Ban; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
# Fail2Ban developers
__copyright__ = "Copyright (c) 2004 Cyril Jaquier; 2012 Yaroslav Halchenko"
__license__ = "GPL"
from __builtin__ import open as fopen
import unittest
import os
import sys
import time
import tempfile
from server.jail import Jail
from server.filterpoll import FilterPoll
from server.filter import FileFilter, DNSUtils
from server.failmanager import FailManager
from server.failmanager import FailManagerEmpty
#
# Useful helpers
#
from utils import mtimesleep
# yoh: per Steven Hiscocks's insight while troubleshooting
# https://github.com/fail2ban/fail2ban/issues/103#issuecomment-15542836
# adding a sufficiently large buffer might help to guarantee that
# writes happen atomically.
def open(*args):
"""Overload built in open so we could assure sufficiently large buffer
Explicit .flush would be needed to assure that changes leave the buffer
"""
if len(args) == 2:
# ~50kB buffer should be sufficient for all tests here.
args = args + (50000,)
return fopen(*args)
def _killfile(f, name):
try:
f.close()
except:
pass
try:
os.unlink(name)
except:
pass
# there might as well be the .bak file
if os.path.exists(name + '.bak'):
_killfile(None, name + '.bak')
def _assert_equal_entries(utest, found, output, count=None):
"""Little helper to unify comparisons with the target entries
and report helpful failure reports instead of millions of seconds ;)
"""
utest.assertEqual(found[0], output[0]) # IP
utest.assertEqual(found[1], count or output[1]) # count
found_time, output_time = \
time.localtime(found[2]),\
time.localtime(output[2])
utest.assertEqual(found_time, output_time)
if len(output) > 3 and count is None: # match matches
# do not check if custom count (e.g. going through them twice)
if os.linesep != '\n' or sys.platform.startswith('cygwin'):
# on those where text file lines end with '\r\n', remove '\r'
srepr = lambda x: repr(x).replace(r'\r', '')
else:
srepr = repr
utest.assertEqual(srepr(found[3]), srepr(output[3]))
def _assert_correct_last_attempt(utest, filter_, output, count=None):
"""Additional helper to wrap most common test case
Test filter to contain target ticket
"""
if isinstance(filter_, DummyJail):
ticket = filter_.getFailTicket()
else:
# when we are testing without jails
ticket = filter_.failManager.toBan()
attempts = ticket.getAttempt()
date = ticket.getTime()
ip = ticket.getIP()
matches = ticket.getMatches()
found = (ip, attempts, date, matches)
_assert_equal_entries(utest, found, output, count)
def _copy_lines_between_files(fin, fout, n=None, skip=0, mode='a', terminal_line=""):
"""Copy lines from one file to another (which might be already open)
Returns open fout
"""
# on older Pythons and on some FSs st_mtime is int, so we should
# give it some time so polling filter could detect the change
mtimesleep()
if isinstance(fin, str): # pragma: no branch - only used with str in test cases
fin = open(fin, 'r')
# Skip
for i in xrange(skip):
_ = fin.readline()
# Read
i = 0
lines = []
while n is None or i < n:
l = fin.readline()
if terminal_line is not None and l == terminal_line:
break
lines.append(l)
i += 1
# Write: all at once and flush
if isinstance(fout, str):
fout = open(fout, mode)
fout.write('\n'.join(lines))
fout.flush()
# to give other threads possibly some time to crunch
time.sleep(0.1)
return fout
#
# Actual tests
#
class IgnoreIP(unittest.TestCase):
def setUp(self):
"""Call before every test case."""
self.filter = FileFilter(None)
def tearDown(self):
"""Call after every test case."""
def testIgnoreIPOK(self):
ipList = "127.0.0.1", "192.168.0.1", "255.255.255.255", "99.99.99.99"
for ip in ipList:
self.filter.addIgnoreIP(ip)
self.assertTrue(self.filter.inIgnoreIPList(ip))
# Test DNS
self.filter.addIgnoreIP("www.epfl.ch")
self.assertTrue(self.filter.inIgnoreIPList("128.178.50.12"))
def testIgnoreIPNOK(self):
ipList = "", "999.999.999.999", "abcdef", "192.168.0."
for ip in ipList:
self.filter.addIgnoreIP(ip)
self.assertFalse(self.filter.inIgnoreIPList(ip))
# Test DNS
self.filter.addIgnoreIP("www.epfl.ch")
self.assertFalse(self.filter.inIgnoreIPList("127.177.50.10"))
class LogFile(unittest.TestCase):
FILENAME = "testcases/files/testcase01.log"
def setUp(self):
"""Call before every test case."""
self.filter = FilterPoll(None)
self.filter.addLogPath(LogFile.FILENAME)
def tearDown(self):
"""Call after every test case."""
pass
#def testOpen(self):
# self.filter.openLogFile(LogFile.FILENAME)
def testIsModified(self):
self.assertTrue(self.filter.isModified(LogFile.FILENAME))
class LogFileMonitor(unittest.TestCase):
"""Few more tests for FilterPoll API
"""
def setUp(self):
"""Call before every test case."""
self.filter = self.name = 'NA'
_, self.name = tempfile.mkstemp('fail2ban', 'monitorfailures')
self.file = open(self.name, 'a')
self.filter = FilterPoll(None)
self.filter.addLogPath(self.name)
self.filter.setActive(True)
self.filter.addFailRegex("(?:(?:Authentication failure|Failed [-/\w+]+) for(?: [iI](?:llegal|nvalid) user)?|[Ii](?:llegal|nvalid) user|ROOT LOGIN REFUSED) .*(?: from|FROM) <HOST>")
def tearDown(self):
_killfile(self.file, self.name)
pass
def isModified(self, delay=2.):
"""Wait up to `delay` sec to assure that it was modified or not
"""
time0 = time.time()
while time.time() < time0 + delay:
if self.filter.isModified(self.name):
return True
time.sleep(0.1)
return False
def notModified(self):
# shorter wait time for not modified status
return not self.isModified(0.4)
def testNewChangeViaIsModified(self):
# it is a brand new one -- so first we think it is modified
self.assertTrue(self.isModified())
# but not any longer
self.assertTrue(self.notModified())
self.assertTrue(self.notModified())
mtimesleep() # to guarantee freshier mtime
for i in range(4): # few changes
# unless we write into it
self.file.write("line%d\n" % i)
self.file.flush()
self.assertTrue(self.isModified())
self.assertTrue(self.notModified())
mtimesleep() # to guarantee freshier mtime
os.rename(self.name, self.name + '.old')
# we are not signaling as modified whenever
# it gets away
self.assertTrue(self.notModified())
f = open(self.name, 'a')
self.assertTrue(self.isModified())
self.assertTrue(self.notModified())
mtimesleep()
f.write("line%d\n" % i)
f.flush()
self.assertTrue(self.isModified())
self.assertTrue(self.notModified())
_killfile(f, self.name)
_killfile(self.name, self.name + '.old')
pass
def testNewChangeViaGetFailures_simple(self):
# suck in lines from this sample log file
self.filter.getFailures(self.name)
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
# Now let's feed it with entries from the file
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, n=5)
self.filter.getFailures(self.name)
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
# and it should have not been enough
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, skip=5)
self.filter.getFailures(self.name)
_assert_correct_last_attempt(self, self.filter, GetFailures.FAILURES_01)
def testNewChangeViaGetFailures_rewrite(self):
#
# if we rewrite the file at once
self.file.close()
_copy_lines_between_files(GetFailures.FILENAME_01, self.name)
self.filter.getFailures(self.name)
_assert_correct_last_attempt(self, self.filter, GetFailures.FAILURES_01)
# What if file gets overridden
# yoh: skip so we skip those 2 identical lines which our
# filter "marked" as the known beginning, otherwise it
# would not detect "rotation"
self.file = _copy_lines_between_files(GetFailures.FILENAME_01, self.name,
skip=3, mode='w')
self.filter.getFailures(self.name)
#self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
_assert_correct_last_attempt(self, self.filter, GetFailures.FAILURES_01)
def testNewChangeViaGetFailures_move(self):
#
# if we move file into a new location while it has been open already
self.file = _copy_lines_between_files(GetFailures.FILENAME_01, self.name,
n=14, mode='w')
self.filter.getFailures(self.name)
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
self.assertEqual(self.filter.failManager.getFailTotal(), 2)
# move aside, but leaving the handle still open...
os.rename(self.name, self.name + '.bak')
_copy_lines_between_files(GetFailures.FILENAME_01, self.name, skip=14)
self.filter.getFailures(self.name)
_assert_correct_last_attempt(self, self.filter, GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 3)
from threading import Lock
from dummyjail import DummyJail
def get_monitor_failures_testcase(Filter_):
"""Generator of TestCase's for different filters/backends
"""
# add Filter_'s name so we could easily identify bad cows
testclass_name = tempfile.mktemp(
'fail2ban', 'monitorfailures_%s' % (Filter_.__name__,))
class MonitorFailures(unittest.TestCase):
count = 0
def setUp(self):
"""Call before every test case."""
self.filter = self.name = 'NA'
self.name = '%s-%d' % (testclass_name, self.count)
MonitorFailures.count += 1 # so we have unique filenames across tests
self.file = open(self.name, 'a')
self.jail = DummyJail()
self.filter = Filter_(self.jail)
self.filter.addLogPath(self.name)
self.filter.setActive(True)
self.filter.addFailRegex("(?:(?:Authentication failure|Failed [-/\w+]+) for(?: [iI](?:llegal|nvalid) user)?|[Ii](?:llegal|nvalid) user|ROOT LOGIN REFUSED) .*(?: from|FROM) <HOST>")
self.filter.start()
# If filter is polling it would sleep a bit to guarantee that
# we have initial time-stamp difference to trigger "actions"
self._sleep_4_poll()
#print "D: started filter %s" % self.filter
def tearDown(self):
#print "D: SLEEPING A BIT"
#import time; time.sleep(5)
#print "D: TEARING DOWN"
self.filter.stop()
#print "D: WAITING FOR FILTER TO STOP"
self.filter.join() # wait for the thread to terminate
#print "D: KILLING THE FILE"
_killfile(self.file, self.name)
#time.sleep(0.2) # Give FS time to ack the removal
pass
def isFilled(self, delay=2.):
"""Wait up to `delay` sec to assure that it was modified or not
"""
time0 = time.time()
while time.time() < time0 + delay:
if len(self.jail):
return True
time.sleep(0.1)
return False
def _sleep_4_poll(self):
# Since FilterPoll relies on time stamps and some
# actions might be happening too fast in the tests,
# sleep a bit to guarantee reliable time stamps
if isinstance(self.filter, FilterPoll):
mtimesleep()
def isEmpty(self, delay=0.4):
# shorter wait time for not modified status
return not self.isFilled(delay)
def assert_correct_last_attempt(self, failures, count=None):
self.assertTrue(self.isFilled(20)) # give Filter a chance to react
_assert_correct_last_attempt(self, self.jail, failures, count=count)
def test_grow_file(self):
# suck in lines from this sample log file
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
# Now let's feed it with entries from the file
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, n=5)
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
# and our dummy jail is empty as well
self.assertFalse(len(self.jail))
# since it should have not been enough
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, skip=5)
self.assertTrue(self.isFilled(6))
# so we sleep for up to 2 sec for it not to become empty,
# and meanwhile pass to other thread(s) and filter should
# have gathered new failures and passed them into the
# DummyJail
self.assertEqual(len(self.jail), 1)
# and there should be no "stuck" ticket in failManager
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(len(self.jail), 0)
#return
# just for fun let's copy all of them again and see if that results
# in a new ban
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, n=100)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
def test_rewrite_file(self):
# if we rewrite the file at once
self.file.close()
_copy_lines_between_files(GetFailures.FILENAME_01, self.name)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
# What if file gets overridden
# yoh: skip so we skip those 2 identical lines which our
# filter "marked" as the known beginning, otherwise it
# would not detect "rotation"
self.file = _copy_lines_between_files(GetFailures.FILENAME_01, self.name,
skip=3, mode='w')
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
def test_move_file(self):
# if we move file into a new location while it has been open already
self.file = _copy_lines_between_files(GetFailures.FILENAME_01, self.name,
n=14, mode='w')
# Poll might need more time
self.assertTrue(self.isEmpty(4 + int(isinstance(self.filter, FilterPoll))*2),
"Queue must be empty but it is not: %s."
% (', '.join([str(x) for x in self.jail.queue])))
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
self.assertEqual(self.filter.failManager.getFailTotal(), 2)
# move aside, but leaving the handle still open...
os.rename(self.name, self.name + '.bak')
_copy_lines_between_files(GetFailures.FILENAME_01, self.name, skip=14)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 3)
# now remove the moved file
_killfile(None, self.name + '.bak')
_copy_lines_between_files(GetFailures.FILENAME_01, self.name, n=100)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 6)
def _test_move_into_file(self, interim_kill=False):
# if we move a new file into the location of an old (monitored) file
_copy_lines_between_files(GetFailures.FILENAME_01, self.name,
n=100).close()
# make sure that it is monitored first
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 3)
if interim_kill:
_killfile(None, self.name)
time.sleep(0.2) # let them know
# now create a new one to override old one
_copy_lines_between_files(GetFailures.FILENAME_01, self.name + '.new',
n=100).close()
os.rename(self.name + '.new', self.name)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 6)
# and to make sure that it now monitored for changes
_copy_lines_between_files(GetFailures.FILENAME_01, self.name,
n=100).close()
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 9)
def test_move_into_file(self):
self._test_move_into_file(interim_kill=False)
def test_move_into_file_after_removed(self):
# exactly as above test + remove file explicitly
# to test against possible drop-out of the file from monitoring
self._test_move_into_file(interim_kill=True)
def test_new_bogus_file(self):
# to make sure that watching whole directory does not effect
_copy_lines_between_files(GetFailures.FILENAME_01, self.name, n=100)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
# create a bogus file in the same directory and see if that doesn't affect
open(self.name + '.bak2', 'w').write('')
_copy_lines_between_files(GetFailures.FILENAME_01, self.name, n=100)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
self.assertEqual(self.filter.failManager.getFailTotal(), 6)
_killfile(None, self.name + '.bak2')
def test_delLogPath(self):
# Smoke test for removing of the path from being watched
# basic full test
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, n=100)
self.assert_correct_last_attempt(GetFailures.FAILURES_01)
# and now remove the LogPath
self.filter.delLogPath(self.name)
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, n=100)
# so we should get no more failures detected
self.assertTrue(self.isEmpty(2))
# but then if we add it back again
self.filter.addLogPath(self.name)
# Tricky catch here is that it should get them from the
# tail written before, so let's not copy anything yet
#_copy_lines_between_files(GetFailures.FILENAME_01, self.name, n=100)
# we should detect the failures
self.assert_correct_last_attempt(GetFailures.FAILURES_01, count=6) # was needed if we write twice above
# now copy and get even more
_copy_lines_between_files(GetFailures.FILENAME_01, self.file, n=100)
# yoh: not sure why count here is not 9... TODO
self.assert_correct_last_attempt(GetFailures.FAILURES_01)#, count=9)
MonitorFailures.__name__ = "MonitorFailures<%s>(%s)" \
% (Filter_.__name__, testclass_name) # 'tempfile')
return MonitorFailures
class GetFailures(unittest.TestCase):
FILENAME_01 = "testcases/files/testcase01.log"
FILENAME_02 = "testcases/files/testcase02.log"
FILENAME_03 = "testcases/files/testcase03.log"
FILENAME_04 = "testcases/files/testcase04.log"
FILENAME_USEDNS = "testcases/files/testcase-usedns.log"
# so that they could be reused by other tests
FAILURES_01 = ('193.168.0.128', 3, 1124013599.0,
['Aug 14 11:59:59 [sshd] error: PAM: Authentication failure for kevin from 193.168.0.128\n']*3)
def setUp(self):
"""Call before every test case."""
self.filter = FileFilter(None)
self.filter.setActive(True)
# TODO Test this
#self.filter.setTimeRegex("\S{3}\s{1,2}\d{1,2} \d{2}:\d{2}:\d{2}")
#self.filter.setTimePattern("%b %d %H:%M:%S")
def tearDown(self):
"""Call after every test case."""
def testGetFailures01(self, filename=None, failures=None):
filename = filename or GetFailures.FILENAME_01
failures = failures or GetFailures.FAILURES_01
self.filter.addLogPath(filename)
self.filter.addFailRegex("(?:(?:Authentication failure|Failed [-/\w+]+) for(?: [iI](?:llegal|nvalid) user)?|[Ii](?:llegal|nvalid) user|ROOT LOGIN REFUSED) .*(?: from|FROM) <HOST>$")
self.filter.getFailures(filename)
_assert_correct_last_attempt(self, self.filter, failures)
def testCRLFFailures01(self):
# We first adjust logfile/failures to end with CR+LF
fname = tempfile.mktemp(prefix='tmp_fail2ban', suffix='crlf')
# poor man unix2dos:
fin, fout = open(GetFailures.FILENAME_01), open(fname, 'w')
for l in fin.readlines():
fout.write('%s\r\n' % l.rstrip('\n'))
fin.close()
fout.close()
# now see if we should be getting the "same" failures
self.testGetFailures01(filename=fname,
failures=GetFailures.FAILURES_01[:3] +
([x.rstrip('\n') + '\r\n' for x in
GetFailures.FAILURES_01[-1]],))
_killfile(fout, fname)
def testGetFailures02(self):
output = ('141.3.81.106', 4, 1124013539.0,
['Aug 14 11:%d:59 i60p295 sshd[12365]: Failed publickey for roehl from ::ffff:141.3.81.106 port 51332 ssh2\n'
% m for m in 53, 54, 57, 58])
self.filter.addLogPath(GetFailures.FILENAME_02)
self.filter.addFailRegex("Failed .* from <HOST>")
self.filter.getFailures(GetFailures.FILENAME_02)
_assert_correct_last_attempt(self, self.filter, output)
def testGetFailures03(self):
output = ('203.162.223.135', 6, 1124013544.0)
self.filter.addLogPath(GetFailures.FILENAME_03)
self.filter.addFailRegex("error,relay=<HOST>,.*550 User unknown")
self.filter.getFailures(GetFailures.FILENAME_03)
_assert_correct_last_attempt(self, self.filter, output)
def testGetFailures04(self):
output = [('212.41.96.186', 4, 1124013600.0),
('212.41.96.185', 4, 1124013598.0)]
self.filter.addLogPath(GetFailures.FILENAME_04)
self.filter.addFailRegex("Invalid user .* <HOST>")
self.filter.getFailures(GetFailures.FILENAME_04)
try:
for i, out in enumerate(output):
_assert_correct_last_attempt(self, self.filter, out)
except FailManagerEmpty:
pass
def testGetFailuresUseDNS(self):
# We should still catch failures with usedns = no ;-)
output_yes = ('93.184.216.119', 2, 1124013539.0,
['Aug 14 11:54:59 i60p295 sshd[12365]: Failed publickey for roehl from example.com port 51332 ssh2\n',
'Aug 14 11:58:59 i60p295 sshd[12365]: Failed publickey for roehl from ::ffff:93.184.216.119 port 51332 ssh2\n'])
output_no = ('93.184.216.119', 1, 1124013539.0,
['Aug 14 11:58:59 i60p295 sshd[12365]: Failed publickey for roehl from ::ffff:93.184.216.119 port 51332 ssh2\n'])
# Actually no exception would be raised -- it will be just set to 'no'
#self.assertRaises(ValueError,
# FileFilter, None, useDns='wrong_value_for_useDns')
for useDns, output in (('yes', output_yes),
('no', output_no),
('warn', output_yes)):
filter_ = FileFilter(None, useDns=useDns)
filter_.setActive(True)
filter_.failManager.setMaxRetry(1) # we might have just few failures
filter_.addLogPath(GetFailures.FILENAME_USEDNS)
filter_.addFailRegex("Failed .* from <HOST>")
filter_.getFailures(GetFailures.FILENAME_USEDNS)
_assert_correct_last_attempt(self, filter_, output)
def testGetFailuresMultiRegex(self):
output = ('141.3.81.106', 8, 1124013541.0)
self.filter.addLogPath(GetFailures.FILENAME_02)
self.filter.addFailRegex("Failed .* from <HOST>")
self.filter.addFailRegex("Accepted .* from <HOST>")
self.filter.getFailures(GetFailures.FILENAME_02)
_assert_correct_last_attempt(self, self.filter, output)
def testGetFailuresIgnoreRegex(self):
output = ('141.3.81.106', 8, 1124013541.0)
self.filter.addLogPath(GetFailures.FILENAME_02)
self.filter.addFailRegex("Failed .* from <HOST>")
self.filter.addFailRegex("Accepted .* from <HOST>")
self.filter.addIgnoreRegex("for roehl")
self.filter.getFailures(GetFailures.FILENAME_02)
self.assertRaises(FailManagerEmpty, self.filter.failManager.toBan)
class DNSUtilsTests(unittest.TestCase):
def testUseDns(self):
res = DNSUtils.textToIp('www.example.com', 'no')
self.assertEqual(res, [])
res = DNSUtils.textToIp('www.example.com', 'warn')
self.assertEqual(res, ['93.184.216.119'])
res = DNSUtils.textToIp('www.example.com', 'yes')
self.assertEqual(res, ['93.184.216.119'])
def testTextToIp(self):
# Test hostnames
hostnames = [
'www.example.com',
'doh1.2.3.4.buga.xxxxx.yyy.invalid',
'1.2.3.4.buga.xxxxx.yyy.invalid',
]
for s in hostnames:
res = DNSUtils.textToIp(s, 'yes')
if s == 'www.example.com':
self.assertEqual(res, ['93.184.216.119'])
else:
self.assertEqual(res, [])
class JailTests(unittest.TestCase):
def testSetBackend_gh83(self):
# smoke test
jail = Jail('test', backend='polling') # Must not fail to initiate