[webkit-dev] Running pixel tests on build.webkit.org

Ojan Vafai ojan at chromium.org
Thu Jan 7 17:01:43 PST 2010

On Thu, Jan 7, 2010 at 10:22 AM, Darin Adler <darin at apple.com> wrote:

> On Jan 7, 2010, at 10:19 AM, Dimitri Glazkov wrote:
> > Are we planning to run pixel tests on the build bots?
> If we can get them green, we should. It’s a lot of work. We need a
> volunteer to do that work. We’ve tried before.

Two possible long-term solutions come to mind:
1. Turn the bots orange on pixel failures. They still need fixing, but are
not as severe as text diff failures. I'm not a huge fan of this, but it's an
2. Add in a concept of expected failures and only turn the bots red for
*unexpected* failurs. More details on this below.

In chromium-land, there's an expectations file that lists expected failures
and allows for distinguishing different types of failures (e.g. IMAGE vs.
TEXT). It's like Skipped lists, but doesn't necessarily skip the test.
Fixing the expected failures still needs doing of course, but can be done
asynchronously. The primary advantage of this approach is that we can turn
on pixel tests, keep the bots green and avoid further regressions.

Would something like that make sense for WebKit as a whole? To be clear, we
would be nearly as loathe to add tests to this file as we are about adding
them to the Skipped lists. This just provides a way forward.

While it's true that the bots used to be red more frequently with pixel
tests turned on, for the most part, there weren't significant pixel
regressions. Now, if you run the pixel tests on a clean build, there are a
number of failures and a very large number of hash-mismatches that are
within the failure tolerance level.


For reference, the format of the expectations file is something like this:

// Fails the image diff but not the text diff.
fast/forms/foo.html = IMAGE

// Fails just the text diff.
fast/forms/bar.html = TEXT

// Fails both the image and text diffs.
fast/forms/baz.html = IMAGE+TEXT

// Skips this test (e.g. because it hangs run-webkit-tests or causes other
tests to fail).
SKIP : fast/forms/foo1.html = IMAGE
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