[webkit-dev] Proposal for Device-Specific Layout Tests

Tue Dec 4 17:17:23 PST 2018

> On Dec 4, 2018, at 4:43 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:
> 
> 
> On Tue, Dec 4, 2018 at 12:55 PM Jonathan Bedard <jbedard at apple.com <mailto:jbedard at apple.com>> wrote:
> These directories would be along-side tests.
> 
> I don't like that platform-specific results are under LayoutTests/platform and device-specific results are next to the tests. We should stick with either convention, not mix them up.
> 
> If we were to match LayoutTests/platforms, we should probably put it under LayoutTests/devices, or alternatively inside each platform's test directory. Alternatively, I'd be fine if we moved platform specific results to those subdirectories. But having both conventions used throughout would be an insane mess.
> 
> It is different from how we treat platforms because platforms have historically been used to differentiate between different binary types, which doesn’t really apply here. We also have platform versions which we use for inheriting expectations between versions, that idea also doesn’t transfer well to the case.
> 
> I don't think these differences are all that interesting. The problem I have with this approach is that this will be yet another concept new contributor has to learn, and yet another layer of abstraction & a new set of configurations we'd have to worry about when figuring out which test expectation will be used & needs to be updated when WebKit's behavior changes.

The platform solution to this has similar problems (as mentioned bellow, combining the results from multiple platforms into a single logical platform). The best we will be able to do here is come up with a system that effects as few tests as possible. The reason I like optionally splitting expected results for a test into a directory is because this idiom transfers well to displaying test failures when a test has run multiple times. I don’t see a good solution to that problem through the platform technique.

> 
> Creating new device-platforms would make EWS and running layout tests locally very confusing
> 
> Why?
>  
> and wouldn’t really solve the run-a-test-twice problem.
> 
> Again, why?

Because if devices are platforms, then 'run-webkit-tests —ios’ needs to run 2 platforms. This is a huge departure from what a ‘platform’ conceptually is. We would need to invent a whole new way to display results, because what a contributor is thinking of as a platform is, in fact, multiple platforms.

> 
> We would have to have an entirely different set of results for each device type, and when running on-device tests, the user would have to be aware enough to use the platform which corresponds to the device (or devices) they had attached. This would be a pretty radical departure from the way things currently work, were iPhone 7 and iPad tests run with the rest of the iOS tests.
> 
> I don't see how treating iPhone 7 as a platform would pose any issue here. It's like a variant of iOS port like Mountain Lion is a variant of macOS port.
> 
> What I also don't understand is what happens when iOS behavior changes between iOS 10 and iOS 11 on iPhone 7. Where would the expected result live for those two operating systems and how are they named?

I think that example illustrates why the platform idiom is not right for handling device specific expected results. Under my proposal, you could place a platform + device specific expectation like so:

        some-dir/
                some-test.html
                some-test-expected.txt
	platform/ios-10/some-dir/some-test-expected/iPhone-7.txt
        platform/ios-11/some-dir/some-test-expected/iPhone-7.txt

Jonathan

> 
> - R. Niwa
> 
>> On Dec 3, 2018, at 6:25 PM, Ryosuke Niwa <rniwa at webkit.org <mailto:rniwa at webkit.org>> wrote:
>> 
>> Are those directories along side tests? If so, that seems very different from the approach we take with platforms. Why the discrepancy?
>> 
>> Can't we just treat them as specific type of iOS platforms?
>> 
>> - R. Niwa
>> 
>> 
>> On Mon, Dec 3, 2018 at 4:05 PM Jonathan Bedard <jbedard at apple.com <mailto:jbedard at apple.com>> wrote:
>> Hello everyone,
>> 
>> I have a proposal to make writing layout tests for specific types of devices more straight-forward.
>> 
>> Currently, we name directories with the beginning of a device name, such as ‘iphone7’ or ‘ipad’ and hope that those directory names match the name of a device type in the associated port’s CUSTOM_DEVICE_CLASS. This causes some problems, however, in a few circumstances. The first problem arises when two ports have associated devices (such as watchOS and iOS), in this case, a directory which maps to a device type on one port might not on another. The second problem is that our current code for managing devices assumes that devices can be booted on-demand, which is not the case in on-device testing, where we need to run different sets of tests depending on the type of device attached. The last (and most important) problem is that we cannot run the same test twice on two different devices in a single test run (ie, run test.html once on an iPhone and once on an iPad).
>> 
>> To resolve this, I propose 3 changes to how we organize layout tests.
>> 
>> 1) Allow *-expected.txt files to be device-specific <https://bugs.webkit.org/show_bug.cgi?id=192162 <https://bugs.webkit.org/show_bug.cgi?id=192162>>
>> 
>> The idea here would be to optionally allow *-expected.txt files to be a directory looking something like this:
>> 
>> dir/
>>     test.html
>>     test-expected/
>>         iPhone-7.txt
>> 
>> Under this scheme, the name of the .txt file would map directly to a device type. Multiple device-specific expectations would be permitted, but making sense of these results requires change #2.
>> 
>> 2) Support multiple results for a specific test <https://bugs.webkit.org/show_bug.cgi?id=192163 <https://bugs.webkit.org/show_bug.cgi?id=192163>>
>> 
>> Similar to #1, we need to allow test results to be attributed to a device type. This would be done with a similar scheme, where results for a test would optionally be saved as a directory looking like this:
>> 
>> dir/
>>     test/
>>         iPhone-7-actual.txt
>>         iPhone-7-diff.txt
>>         iPhone-7-expected.txt
>>         iPhone-7-diff.html
>>         iPhone-8-actual.txt
>>         iPhone-8-diff.txt
>>         iPhone-8-expected.txt
>>         iPhone-8-diff.html
>> 
>> When reporting, results would be reported to as a new ‘queue’ of the form '<queue>-<device>’.
>> 
>> 3) Provide device specific tags in test expectations <https://bugs.webkit.org/show_bug.cgi?id=192164 <https://bugs.webkit.org/show_bug.cgi?id=192164>>
>> 
>> We already have Debug/Release as well as version tags in our test expectations. The addition here would be device-type tags, those tags would look like this:
>> 
>> [ iPhone 7 ] dir/test.html [ Pass ]
>> [ iPad ] dir/other-test.html [ Pass ]
>> 
>> These tags would allow for 2 features. The first is similar to existing tags, allowing a certain test (or group of tests) to have different expectations or to be skipped entirely on certain device types. The second feature allows for tests and groups of tests to be run on multiple different devices in a single instantiation of run-webkit-tests. For example,
>> 
>> [ iPhone 7, iPad ] dir/some-dir/ [ Pass ]
>> 
>> would indicate that every test in dir/some-dir/ will be run on BOTH iPhone 7 and iPad.
>> 
>> I would welcome anyone else’s thoughts on this.
>> 
>> Jonathan
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