The following layout tests are failing on Sierra Release WK1 These tests fail in succession randomly imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/close.https.html imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/extendable-message-event-constructor.https.html imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/extendable-message-event.https.html imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/postmessage.https.html imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/registration-attribute.https.html imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/service-worker-error-event.https.html imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/unregister.https.html Probable cause: Test history shows these tests have all failed at the same time twice so far with 15 successful runs in-between. They all have a Harness Timeout issue. Example: --- /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/close.https-expected.txt +++ /Volumes/Data/slave/sierra-release-tests-wk2/build/layout-test-results/imported/w3c/web-platform-tests/service-workers/service-worker/ServiceWorkerGlobalScope/close.https-actual.txt @@ -1,4 +1,5 @@ -PASS ServiceWorkerGlobalScope: close operation -PASS ServiceWorkerGlobalScope close operation +Harness Error (TIMEOUT), message = null +TIMEOUT ServiceWorkerGlobalScope: close operation Test timed out + I do not have a regression point yet or repro steps. First failure was in https://build.webkit.org/builders/Apple%20Sierra%20Release%20WK2%20(Tests)/builds/10842. I assume that something is setting a state for all 7 tests. Flakiness Dashboard: https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fclose.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fextendable-message-event-constructor.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fextendable-message-event.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fpostmessage.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fregistration-attribute.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Fservice-worker-error-event.https.html%20imported%2Fw3c%2Fweb-platform-tests%2Fservice-workers%2Fservice-worker%2FServiceWorkerGlobalScope%2Funregister.https.html