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Re: testharness.js v. reftests for rendering tests

From: Simon Pieters <simonp@opera.com>
Date: Tue, 20 Dec 2016 13:18:19 +0100
To: public-test-infra@w3.org, "Geoffrey Sneddon" <me@gsnedders.com>
Message-ID: <op.ysrq4tofidj3kv@simons-mbp>
On Tue, 20 Dec 2016 13:03:02 +0100, Geoffrey Sneddon <me@gsnedders.com>  

> Hi,
> As far as I'm aware, we have no real defined policy as to how rendering
> tests should be written. We essentially have two options: testharness.js
> using the CSSOM or reftests.
> I believe the current Blink policy is to use the former except when
> testing paint code, and Gecko's is to use reftests for both.
> On the whole, despite the performance penalty, I'd much favour
> recommending reftests for both given the intrinsic link between
> rendering and painting and the various optimisations different
> implementations do to avoid invoking the various parts with different
> mutations.
> Of course, if someone thinks the performance penalty is too high maybe
> we'll have to reconsider.
> /gsnedders

I don't have a strong opinion about policy but I will point out that it  
can sometimes be useful to test both. Equivalent CSSOM does not  
necessarily mean equivalent rendering and vice versa.

As an example, for testing the UA stylesheet, it seems most useful to  
first test the CSSOM for everything. But reftests can be useful for e.g.  
testing interaction of writing modes and form controls, or margin  
collapsing quirks, <ol> numbering, framesets, etc.

Simon Pieters
Opera Software
Received on Tuesday, 20 December 2016 12:19:05 UTC

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