The test sometimes fails with the following output: Diff: https://build.webkit.org/results/WPE-Linux-64-bit-Release-Tests/r270360%20(21308)/imported/w3c/web-platform-tests/webxr/xrSession_cancelAnimationFrame_invalidhandle.https-diff.txt --- /home/buildbot/worker/wpe-linux-64-release-tests/build/layout-test-results/imported/w3c/web-platform-tests/webxr/xrSession_cancelAnimationFrame_invalidhandle.https-expected.txt +++ /home/buildbot/worker/wpe-linux-64-release-tests/build/layout-test-results/imported/w3c/web-platform-tests/webxr/xrSession_cancelAnimationFrame_invalidhandle.https-actual.txt @@ -1,3 +1,6 @@ +CONSOLE MESSAGE: SyntaxError: Can't create duplicate variable: 'isChromiumBased' + +Harness Error (FAIL), message = SyntaxError: Can't create duplicate variable: 'isChromiumBased' PASS XRSession cancelAnimationFrame does not have unexpected behavior when given invalid handles on immersive testSession PASS XRSession cancelAnimationFrame does not have unexpected behavior when given invalid handles on non-immersive testSession It's possible to reproduce the failure with the following command: $ Tools/Scripts/run-webkit-tests --wpe --release --iterations=3 imported/w3c/web-platform-tests/webxr/xrSession_cancelAnimationFrame_invalidhandle.https.html I think the problem is in https://webkit-search.igalia.com/webkit/source/LayoutTests/imported/w3c/web-platform-tests/webxr/resources/webxr_util.js#22, that block of code is meant to be executed only once but sometimes is executed more than once.