test_antistampede fails intermittently

[jaraco]

See this test failure where test_antistampede fails with an AssertionError:

_________________________ CacheTest.test_antistampede __________________________

self = <cherrypy.test.test_caching.CacheTest testMethod=test_antistampede>

    def test_antistampede(self):

        SECONDS = 4

        slow_url = '/long_process?seconds={SECONDS}'.format(**locals())

        # We MUST make an initial synchronous request in order to create the

        # AntiStampedeCache object, and populate its selecting_headers,

        # before the actual stampede.

        self.getPage(slow_url)

        self.assertBody('success!')

        self.getPage('/clear_cache?path=' + quote(slow_url, safe=''))

        self.assertStatus(200)

    

        start = datetime.datetime.now()

    

        def run():

            self.getPage(slow_url)

            # The response should be the same every time

            self.assertBody('success!')

        ts = [threading.Thread(target=run) for i in xrange(100)]

        for t in ts:

            t.start()

        for t in ts:

            t.join()

        finish = datetime.datetime.now()

        # Allow for overhead, two seconds for slow hosts

        allowance = SECONDS + 2

>       self.assertEqualDates(start, finish, seconds=allowance)

cherrypy/test/test_caching.py:317: 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <cherrypy.test.test_caching.CacheTest testMethod=test_antistampede>

dt1 = datetime.datetime(2016, 12, 23, 22, 18, 48, 495204)

dt2 = datetime.datetime(2016, 12, 23, 22, 18, 55, 718969), seconds = 6

    def assertEqualDates(self, dt1, dt2, seconds=None):

        """Assert abs(dt1 - dt2) is within Y seconds."""

        if seconds is None:

            seconds = self.date_tolerance

    

        if dt1 > dt2:

            diff = dt1 - dt2

        else:

            diff = dt2 - dt1

        if not diff < datetime.timedelta(seconds=seconds):

            raise AssertionError('%r and %r are not within %r seconds.' %

>                                (dt1, dt2, seconds))

E           AssertionError: datetime.datetime(2016, 12, 23, 22, 18, 48, 495204) and datetime.datetime(2016, 12, 23, 22, 18, 55, 718969) are not within 6 seconds.

cherrypy/test/helper.py:403: AssertionError

[mgorny]

Now that xfail_strict has been enabled in 565c181, this XFAIL is causing test failure when the test passes (and it seems to pass for me all the time).

[webknjaz]

@mgorny @jaraco FYI for flaky tests, the right solution is to have @pytest.mark.xfail(..., strict=False)