| commit | 74e1fe40eb227423537d6eafa99244ece1a8f8fd | [log] [tgz] |
|---|---|---|
| author | Dominic Farolino <dom@chromium.org> | Tue Mar 17 06:58:38 2020 |
| committer | Blink WPT Bot <blink-w3c-test-autoroller@chromium.org> | Tue Mar 17 07:18:36 2020 |
| tree | 9f7b2fdb70674a5bf470f0014cd93aa09e873b83 | |
| parent | 769ccd7a7919968ac494aca0ca7467ce3d90a646 [diff] |
Referrer-WPT: Fix weird referrer test timing issue This CL fixes a very tricky timing issue I grappled with debugging: I noticed that a non-deterministic amount of the worklet-referrer tests always failed in Chromium when run from the wpt.live site, e.g., https://wpt.live/worklets/paint-worklet-referrer.https.html. This was NOT reproducible locally via any of the following: a.) `./wpt serve` and running the tests in Chromium b.) run_web_tests.py to run them automatically with Chromium I made a dummy WPT PR [1] just to trigger a wpt.live deployment so I could debug my changes in the wpt.live environment, where the tests were failing for some reason. The main referrer test window opens up a bunch of child windows which run a test, and report their results back to the main window IN ORDER. The test were failing for two reasons: - assert_equals: expected "LOADED" but got "RESOLVED" - assert_equals: expected (string) "RESOLVED" but got (object) object "[object Object]" This indicated some type of timing issue between the child windows, and I suspected that one window was reporting back its results when the main window was expecting a different child's results. I dug into the second assertion failure above, logging the "object". It was a timeout object automatically reported by the testharness. This made me think that the child windows were being kept open too long after their test finished, and automatically reported an "extra" timeout object back to the main window, when it was expecting a later child window's results. I finally realized that on line 3, there was a call `add_completion_callback(() => win.close())`, the intention being to close a child window after its test completed. I found in the testharness API docs, that add_completion_callback doesn't call the callback after the test completes, but only after *all* tests complete [2]. This means all child windows were being kept open for the entire duration of the main test. This caused some child windows to report the timeout object to the main window when the server is slow, like on the wpt.live site, but never was reproduced. The fix is to not use add_completion_callback. We could instead use add_result_callback which would work, but it is global, so it would end up attempting to invoke window.close O(n^2) times for O(n) tests (I've confirmed this). The best solution is to plumb each promise_test object through, and add a cleanup callback that closes the child window. This CL implements that. With this fixed, it might save a lot of debugging hours in the future \o/. [1]: https://github.com/web-platform-tests/wpt/pull/22269 [2]: https://web-platform-tests.org/writing-tests/testharness-api.html#callback-api R=nhiroki@chromium.org Bug: N/A Change-Id: Icac7e58a5bfc218a86549f11804b2bc856b815f6 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2103999 Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org> Commit-Queue: Dominic Farolino <dom@chromium.org> Cr-Commit-Position: refs/heads/master@{#750878}
The web-platform-tests Project is a cross-browser test suite for the Web-platform stack. Writing tests in a way that allows them to be run in all browsers gives browser projects confidence that they are shipping software that is compatible with other implementations, and that later implementations will be compatible with their implementations. This in turn gives Web authors/developers confidence that they can actually rely on the Web platform to deliver on the promise of working across browsers and devices without needing extra layers of abstraction to paper over the gaps left by specification editors and implementors.
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