[webkit-dev] DRT/WTR should clear the cache at the beginning of each test?

Brian Holt brian.holt at samsung.com
Fri Oct 26 03:27:27 PDT 2012

I'm happy to take a look at clearing the cache for the GTK+ port, but I
won't be able to do anything for mac unfortunately.




From: webkit-dev-bounces at lists.webkit.org
[mailto:webkit-dev-bounces at lists.webkit.org] On Behalf Of Ami Fischman
Sent: 26 October 2012 09:20
To: Dirk Pranke
Cc: Adam Barth; WebKit Development
Subject: Re: [webkit-dev] DRT/WTR should clear the cache at the beginning of
each test?


This thread stalled out because although there seemed to be majority
agreement that hermetic/repeatable tests are a good thing, there was a
requirement that all ports be updated to the new behavior at the same time,
and I'm only competent to do the chromium DRT (see
https://bugs.webkit.org/show_bug.cgi?id=93195 for details).


Is anyone interested in stepping up and doing the equivalent (clear caches
between tests) for the mac and/or gtk ports' DRTs?


On Wed, Aug 8, 2012 at 2:35 PM, Dirk Pranke <dpranke at chromium.org> wrote:

On Wed, Aug 8, 2012 at 10:47 AM, Ojan Vafai <ojan at chromium.org> wrote:

> See https://bugs.webkit.org/show_bug.cgi?id=93195.
> media/W3C/video/networkState/networkState_during_progress.html and
> media/video-poster-blocked-by-willsendrequest.html are flaky on all
> platforms because they behave differently if the loaded resource is
> Every time I've taken a stab at reducing test flakiness, I've come across
> least a few tests that pass when run as part of the test suite, but fail
> when run by themselves (or in parallel) because they accidentally expect
> image or something to be in the cache.
> I think it would make the tests more maintainable if we cleared the cache
> before each test run. This is *not* before each page load though. So tests
> that do multiple page loads will still test cross-navigation caching
> behavior.
> While it's true that we could one-off fix each of these tests, it's
> very time consuming to figure out that caching is the problem, that's
> assuming anyone takes the time to look into why the test is flaky in the
> first place.
> Any objections?

Given that the way we run tests in parallel in NRWT means that
different processes get different lists of tests each time, it sounds
like we may be getting a fair amount of nondeterminism from the cache
not being cleared between tests. That seems bad, so I'm in favor of
clearing the cache :)

-- Dirk


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