[webkit-dev] run-webkit-tests question; hashes when comparing ref test output

Ryosuke Niwa rniwa at webkit.org
Fri Jan 23 10:01:51 PST 2015

On Friday, January 23, 2015, Darin Adler <darin at apple.com> wrote:

> > On Jan 22, 2015, at 10:36 PM, Alexey Proskuryakov <ap at webkit.org
> <javascript:;>> wrote:
> >
> >> 22 янв. 2015 г., в 17:57, Darin Adler <darin at apple.com <javascript:;>>
> написал(а):
> >>
> >> What about the test I cited?
> >>
> >> svg/css/svg-resource-fragment-identifier-img-src.html
> >
> > This particular test is buggy - it is a hidpi test, so it dumps results
> as a 1600x1200 image, but its -expected.html is not hidpi, and is dumped as
> 800x600, so hashes are obviously different. I now filed <
> https://bugs.webkit.org/show_bug.cgi?id=140815> about this test.
> >
> > When we compare pixels, we draw both images into bitmaps of the same
> size, so they become similar enough for ImageDiff to consider them
> identical.
> >
> > Earlier today, Simon and I agreed that we should just silence the error
> message, because it only tells us about minor color differences that are
> inevitable when comparing compositing vs. non-compositing. Looks like it
> tells us about more actionable issues, too. Also, I just found <
> https://bugs.webkit.org/show_bug.cgi?id=69444>, and I think that its
> rationale applies in this case, too.
> >
> > So we should probably keep this error message. I'm not sure whether we
> should make it a hard error though.
> I think that to improve things we should make an informative message for
> this particular mistake where the expected file has the wrong size or
> resolution.
> For me, the bad thing about the current message is not simply that it’s a
> false positive, but that it’s an unclear error message that covers too many
> different possibilities.
> I’m not sure that keeping things as is will be a good strategy. A message
> that is often expected but sometimes indicates a real problem is not good
> for the project. The average engineer has no idea whether to ignore these
> or act on them!

We could add a new test expectation like ImageDiff to suppress these or we
could expose a new internals or testRunner methods to mark a test as such.

 - R. Niwa

- R. Niwa
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